Systems and methods for single cell processing

ABSTRACT

The present disclosure provides systems and methods for measuring one or more analytes at the single cell level. In some instances, sequencing of a composite barcode sequence may identify a type of analyte, identify a cell, and determine that the type of analyte originated from the cell. In some instances, a probability that a type of analyte originated from the cell may be determined. Multiple types of analytes may be identified to have originated from the cell, and/or the respective probabilities determined. An analyte may be a protein, such as a surface-bound protein or an internal protein. An analyte may be a metabolite or other small molecule. An analyte may be any constituent of a cell.

CROSS-REFERENCE

This application is a continuation of International Application No.PCT/US2018/064763, filed Dec. 10, 2018, which claims the benefit of U.S.Provisional Patent Application No. 62/597,578, filed Dec. 12, 2017 whichapplications are entirely incorporated herein by reference.

BACKGROUND

Samples may be processed for various purposes, such as identification ofa type of moiety or analyte within the sample. The sample may be abiological sample. The biological samples may be processed for variouspurposes, such as detection of a disease (e.g., cancer) oridentification of a particular species. There are various approaches forprocessing samples, such as polymerase chain reaction (PCR) andsequencing.

Biological samples may be processed within various reactionenvironments, such as partitions. Partitions may be wells or droplets.Droplets or wells may be employed to process biological samples in amanner that enables the biological samples to be partitioned andprocessed separately. For example, such droplets may be fluidicallyisolated from other droplets, enabling accurate control of respectiveenvironments in the droplets.

Biological samples in partitions may be subjected to various processes,such as chemical processes or physical processes. Samples in partitionsmay be subjected to heating or cooling, or chemical reactions, such asto yield species that may be qualitatively or quantitatively processed.

SUMMARY

During processing, it may be difficult to identify the origin (e.g.,cell) of an isolated analyte (e.g., protein, metabolite, nucleic acidmolecule, etc.). Recognized herein is a need for systems and methods forprocessing that efficiently and accurately measure one or more analytesat the single cell level. The systems and methods may identify theorigin(s) of one or more analytes. For example, the analyte can be aprotein (e.g., surface-bound protein, internal protein, etc.). Theanalyte can be a metabolite (e.g., alcohol, amino acid, nucleotide,antioxidant, organic acid, polyol, vitamin, cofactor, etc.). The analytecan be any constituent of a cell. The analyte can be a targeted analyte,such as having binding specificity to an antibody that is specificallycaptured and analyzed. The analyte can be a non-targeted analyte that isnon-specifically captured and analyzed.

In an aspect, provided is a method for identifying a protein within acell containing or suspected of containing the protein, comprising: (a)bringing a cell bead generated from the cell in contact with an antibodyhaving binding specificity with the protein, under conditions sufficientto permit the antibody to flow into the cell bead and couple to theprotein, wherein the antibody is coupled to a first nucleic acid barcodemolecule comprising a first nucleic acid sequence; (b) co-partitioningthe cell bead and a bead in a partition, wherein the bead comprises asecond nucleic acid barcode molecule comprising a second nucleic acidsequence; (c) using the first nucleic acid barcode molecule and thesecond nucleic acid barcode molecule to generate a nucleic acid moleculecomprising the first nucleic acid sequence and the second nucleic acidsequence; (d) sequencing the nucleic acid molecule or derivative thereofto identify the first nucleic acid sequence and the second nucleic acidsequence, wherein the first nucleic acid sequence identifies the proteinand the second nucleic acid sequence identifies the cell bead; and (e)determining that the protein originated from within the cell.

In some embodiments, the method further comprises, subsequent to (a),washing out unbound antibodies from the cell bead.

In some embodiments, the cell is lysed in the cell bead.

In some embodiments, the bead is a gel bead.

In some embodiments, the partition is a droplet in an emulsion.

In some embodiments, the second nucleic acid molecule is releasablycoupled to the bead. In some embodiments, the method further comprisesreleasing the second nucleic acid barcode molecule from the bead.

In some embodiments, the bead comprises a plurality of nucleic acidbarcode molecules, each of the plurality of nucleic acid barcodemolecules comprising the second nucleic acid sequence. In someembodiments, each of the plurality of nucleic acid barcode moleculescomprises a unique nucleic acid sequence that is unique to the each ofthe plurality of nucleic acid barcode molecules.

In some embodiments, (a) comprises bringing the cell bead in contactwith a plurality of different antibodies each having binding specificitywith a different protein, wherein a given antibody of the plurality ofdifferent antibodies is coupled to a nucleic acid barcode moleculecomprising a nucleic acid sequence that identifies the given antibody.In some embodiments, the cell bead comprises a plurality of differentproteins from the cell, wherein (d) comprises identifying the differentproteins, and wherein (e) comprises determining that the differentproteins originated from within the cell.

In some embodiments, the determining comprises determining a probabilitythat the protein originated from within the cell.

In another aspect, provided is a method for identifying a protein from acell containing or suspected of containing the protein, comprising: (a)co-partitioning the cell and a bead in a first partition, wherein thebead comprises a plurality of antibodies configured to couple toproteins, wherein each antibody of the plurality of antibodies iscoupled to a first nucleic acid barcode molecule comprising a firstnucleic acid sequence; (b) subjecting the cell to conditions sufficientto permit an antibody of the plurality of antibodies to couple to theprotein to generate a protein-antibody complex comprising the firstnucleic acid barcode molecule; (c) co-partitioning the protein-antibodycomplex in a second partition with a second nucleic acid barcodemolecule comprising a second nucleic acid sequence under conditionssufficient to permit the first nucleic acid barcode molecule of theprotein-antibody complex and the second nucleic acid barcode molecule togenerate a nucleic acid molecule comprising the first nucleic acidsequence and the second nucleic acid sequence; (d) sequencing thenucleic acid molecule or derivative thereof to identify the firstnucleic acid sequence and the second nucleic acid sequence, wherein thefirst nucleic acid sequence identifies the cell and the second nucleicacid sequence identifies the protein; and (e) determining that theprotein originated from the cell.

In some embodiments, the plurality of antibodies is configured to couplenon-specifically to proteins.

In some embodiments, the first partition is a droplet.

In some embodiments, the second partition is a well.

In some embodiments, (b) comprises lysing the cell in the firstpartition.

In some embodiments, a given antibody of the plurality of antibodies iscoupled to a nucleic acid barcode molecule comprising a nucleic acidsequence that is unique to the given antibody.

In some embodiments, the bead is a gel bead.

In some embodiments, the plurality of antibodies is releasably coupledto the bead. In some embodiments, the method further comprises releasingthe plurality of antibodies from the bead.

In some embodiments, the method further comprises, subsequent to (b),separating a first set of protein-antibody complexes comprising a typeof the protein from other protein-antibody complexes comprising othertypes of proteins, wherein the first set of protein-antibody complexescomprises the protein-antibody complex. In some embodiments, the firstset of protein-antibody complexes comprises proteins from a plurality ofcells, wherein the plurality of cells comprises the cell.

In some embodiments, the protein is from within the cell.

In some embodiments, the protein is a surface bound protein.

In some embodiments, the determining comprises determining a probabilitythat the protein originated from within the cell.

In another aspect, provided is a method for identifying a metabolitewithin a cell containing or suspected of containing the metabolite,comprising: (a) bringing a cell bead generated from the cell in contactwith an antibody having binding specificity with the metabolite, underconditions sufficient to permit the antibody to flow into the cell beadand couple to the metabolite, wherein the antibody is coupled to a firstnucleic acid barcode molecule comprising a first nucleic acid sequence;(b) co-partitioning the cell bead and a bead in a partition, wherein thebead comprises a second nucleic acid barcode molecule comprising asecond nucleic acid; (c) using the first nucleic acid barcode moleculeand the second nucleic acid barcode molecule to generate a nucleic acidmolecule comprising the first nucleic acid sequence and the secondnucleic acid sequence; (d) sequencing the nucleic acid molecule toidentify the first nucleic acid sequence and the second nucleic acidsequence, wherein the first nucleic acid sequence identifies themetabolite and the second nucleic acid sequence identifies the cellbead; and (e) determining that the metabolite originated from within thecell.

In some embodiments, the metabolite comprises a structural unit havingbinding specificity to the antibody.

In some embodiments, the metabolite is selected from the groupconsisting of an alcohol, amino acid, nucleotide, antioxidant, organicacid, polyol, and vitamin.

In some embodiments, the metabolite is from a class of metabolites.

In some embodiments, the metabolite is a cofactor.

In some embodiments, the method further comprises, subsequent to (a),washing out unbound antibodies from the cell bead.

In some embodiments, the cell is lysed in the cell bead.

In some embodiments, the bead is a gel bead.

In some embodiments, the partition is a droplet in an emulsion.

In some embodiments, the second nucleic acid molecule is releasablycoupled to the bead. In some embodiments, the method further comprisesreleasing the second nucleic acid barcode molecule from the bead.

In some embodiments, the bead comprises a plurality of nucleic acidbarcode molecules, each of the plurality of nucleic acid barcodemolecules comprising the second nucleic acid sequence. In someembodiments, each of the plurality of nucleic acid barcode moleculescomprises a unique nucleic acid sequence that is unique to the each ofthe plurality of nucleic acid barcode molecules.

In some embodiments, the determining comprises determining a probabilitythat the metabolite originated from within the cell.

In another aspect, provided is a method for determining that a firstanalyte and a second analyte originated from a cell, wherein the firstanalyte is from a surface of the cell and the second analyte is fromwithin the cell, comprising: (a) processing the cell or cell derivativewith a first antibody under conditions sufficient to permit the firstantibody to couple to the first analyte, wherein the first antibodycomprises a first nucleic acid barcode molecule comprising a firstnucleic acid sequence; (b) processing the cell or cell derivative with asecond antibody under conditions sufficient to permit the secondantibody to couple to the second analyte, wherein the second antibodycomprises a second nucleic acid barcode molecule comprising a secondnucleic acid sequence; (c) using the first nucleic acid barcode moleculeand the second nucleic acid barcode molecule to generate a first nucleicacid molecule and a second nucleic acid molecule, respectively, whereinthe first nucleic acid molecule comprises the first nucleic acidsequence and a common barcode sequence and the second nucleic acidmolecule comprises the second nucleic acid sequence and the commonbarcode sequence, wherein the common barcode sequence identifies thecell or cell derivative; (d) sequencing the first nucleic acid moleculeand the second nucleic acid molecule, or derivatives thereof, toidentify the first nucleic acid sequence, the second nucleic acidsequence, and the common barcode sequence, wherein the first nucleicacid sequence identifies the first analyte, the second nucleic acidsequence identifies the second analyte, and the common barcode sequenceidentifies the cell or cell derivative; and (e) determining that thefirst analyte and the second analyte originated from the cell.

In some embodiments, the first analyte and the second analyte aredifferent types of analytes.

In some embodiments, the first analyte and the second analyte are thesame type of analyte.

In some embodiments, the first analyte and/or the second analyte is aprotein.

In some embodiments, the second analyte is a metabolite.

In some embodiments, (a) comprises processing the cell and (b) compriseprocessing the cell derivative. In some embodiments, the cell derivativeis a cell bead.

In some embodiments, (c) is performed by co-partitioning the cell orcell derivative with a plurality of barcode molecules each comprisingthe common barcode sequence. In some embodiments, the plurality ofbarcode molecules is coupled to a bead.

In some embodiments, the determining comprises determining a probabilitythat the first analyte or the second analyte originated from the cell.

In some embodiments, the determining comprises determining a firstprobability that the first analyte originated from the cell anddetermining a second probability that the second analyte originated fromwithin the cell.

Additional aspects and advantages of the present disclosure will becomereadily apparent to those skilled in this art from the followingdetailed description, wherein only illustrative embodiments of thepresent disclosure are shown and described. As will be realized, thepresent disclosure is capable of other and different embodiments, andits several details are capable of modifications in various obviousrespects, all without departing from the disclosure. Accordingly, thedrawings and description are to be regarded as illustrative in nature,and not as restrictive.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.To the extent publications and patents or patent applicationsincorporated by reference contradict the disclosure contained in thespecification, the specification is intended to supersede and/or takeprecedence over any such contradictory material.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings (also “Figure” and “FIG.” herein), of which:

FIG. 1 shows an example of a microfluidic channel structure forpartitioning individual biological particles.

FIG. 2 shows an example of a microfluidic channel structure fordelivering barcode carrying beads to droplets.

FIG. 3 shows an example of a microfluidic channel structure forco-partitioning biological particles and reagents.

FIG. 4 shows an example of a microfluidic channel structure for thecontrolled partitioning of beads into discrete droplets.

FIG. 5 shows an example of a microfluidic channel structure forincreased droplet generation throughput.

FIG. 6 shows another example of a microfluidic channel structure forincreased droplet generation throughput.

FIG. 7A shows a cross-section view of another example of a microfluidicchannel structure with a geometric feature for controlled partitioning.FIG. 7B shows a perspective view of the channel structure of FIG. 7A.

FIG. 8 illustrates an example of a barcode carrying bead.

FIG. 9 illustrates a method for identifying and measuring an analyte ina cell.

FIG. 10 illustrates another method for identifying and measuring ananalyte in a cell.

FIG. 11 shows a computer system that is programmed or otherwiseconfigured to implement methods provided herein.

DETAILED DESCRIPTION

While various embodiments of the invention have been shown and describedherein, it will be obvious to those skilled in the art that suchembodiments are provided by way of example only. Numerous variations,changes, and substitutions may occur to those skilled in the art withoutdeparting from the invention. It should be understood that variousalternatives to the embodiments of the invention described herein may beemployed.

Where values are described as ranges, it will be understood that suchdisclosure includes the disclosure of all possible sub-ranges withinsuch ranges, as well as specific numerical values that fall within suchranges irrespective of whether a specific numerical value or specificsub-range is expressly stated.

The term “barcode,” as used herein, generally refers to a label, oridentifier, that conveys or is capable of conveying information about ananalyte. A barcode can be part of an analyte. A barcode can beindependent of an analyte. A barcode can be a tag attached to an analyte(e.g., nucleic acid molecule) or a combination of the tag in addition toan endogenous characteristic of the analyte (e.g., size of the analyteor end sequence(s)). A barcode may comprise a plurality of barcode unitsor elements. A barcode may be unique. Barcodes can have a variety ofdifferent formats. For example, barcodes can include: polynucleotidebarcodes; random nucleic acid and/or amino acid sequences; and syntheticnucleic acid and/or amino acid sequences. A barcode can be attached toan analyte in a reversible or irreversible manner. A barcode can beadded to, for example, a fragment of a deoxyribonucleic acid (DNA) orribonucleic acid (RNA) sample before, during, and/or after sequencing ofthe sample. Barcodes can allow for identification and/or quantificationof individual sequencing-reads.

The term “real time,” as used herein, can refer to a response time ofless than about 1 second, a tenth of a second, a hundredth of a second,a millisecond, or less. The response time may be greater than 1 second.In some instances, real time can refer to simultaneous or substantiallysimultaneous processing, detection or identification.

The term “subject,” as used herein, generally refers to an animal, suchas a mammal (e.g., human) or avian (e.g., bird), or other organism, suchas a plant. For example, the subject can be a vertebrate, a mammal, arodent (e.g., a mouse), a primate, a simian or a human. Animals mayinclude, but are not limited to, farm animals, sport animals, and pets.A subject can be a healthy or asymptomatic individual, an individualthat has or is suspected of having a disease (e.g., cancer) or apre-disposition to the disease, and/or an individual that is in need oftherapy or suspected of needing therapy. A subject can be a patient. Asubject can be a microorganism or microbe (e.g., bacteria, fungi,archaea, viruses).

The term “genome,” as used herein, generally refers to genomicinformation from a subject, which may be, for example, at least aportion or an entirety of a subject's hereditary information. A genomecan be encoded either in DNA or in RNA. A genome can comprise codingregions (e.g., that code for proteins) as well as non-coding regions. Agenome can include the sequence of all chromosomes together in anorganism. For example, the human genome ordinarily has a total of 46chromosomes. The sequence of all of these together may constitute ahuman genome.

The terms “adaptor(s)”, “adapter(s)” and “tag(s)” may be usedsynonymously. An adaptor or tag can be coupled to a polynucleotidesequence to be “tagged” by any approach, including ligation,hybridization, or other approaches.

The term “sequencing,” as used herein, generally refers to methods andtechnologies for determining the sequence of nucleotide bases in one ormore polynucleotides. The polynucleotides can be, for example, nucleicacid molecules such as deoxyribonucleic acid (DNA) or ribonucleic acid(RNA), including variants or derivatives thereof (e.g., single strandedDNA). Sequencing can be performed by various systems currentlyavailable, such as, without limitation, a sequencing system byIllumina®, Pacific Biosciences (PacBio®), Oxford Nanopore®, or LifeTechnologies (Ion Torrent®). Alternatively or in addition, sequencingmay be performed using nucleic acid amplification, polymerase chainreaction (PCR) (e.g., digital PCR, quantitative PCR, or real time PCR),or isothermal amplification. Such systems may provide a plurality of rawgenetic data corresponding to the genetic information of a subject(e.g., human), as generated by the systems from a sample provided by thesubject. In some examples, such systems provide sequencing reads (also“reads” herein). A read may include a string of nucleic acid basescorresponding to a sequence of a nucleic acid molecule that has beensequenced. In some situations, systems and methods provided herein maybe used with proteomic information.

The term “bead,” as used herein, generally refers to a particle. Thebead may be a solid or semi-solid particle. The bead may be a gel bead.The gel bead may include a polymer matrix (e.g., matrix formed bypolymerization or cross-linking). The polymer matrix may include one ormore polymers (e.g., polymers having different functional groups orrepeat units). Polymers in the polymer matrix may be randomly arranged,such as in random copolymers, and/or have ordered structures, such as inblock copolymers. Cross-linking can be via covalent, ionic, orinductive, interactions, or physical entanglement. The bead may be amacromolecule. The bead may be formed of nucleic acid molecules boundtogether. The bead may be formed via covalent or non-covalent assemblyof molecules (e.g., macromolecules), such as monomers or polymers. Suchpolymers or monomers may be natural or synthetic. Such polymers ormonomers may be or include, for example, nucleic acid molecules (e.g.,DNA or RNA). The bead may be formed of a polymeric material. The beadmay be magnetic or non-magnetic. The bead may be rigid. The bead may beflexible and/or compressible. The bead may be disruptable ordissolvable. The bead may be a solid particle (e.g., a metal-basedparticle including but not limited to iron oxide, gold or silver)covered with a coating comprising one or more polymers. Such coating maybe disruptable or dissolvable.

The term “sample,” as used herein, generally refers to a biologicalsample of a subject. The biological sample may comprise any number ofmacromolecules, for example, cellular macromolecules. The sample may bea cell sample. The sample may be a cell line or cell culture sample. Thesample can include one or more cells. The sample can include one or moremicrobes. The biological sample may be a nucleic acid sample or proteinsample. The biological sample may also be a carbohydrate sample or alipid sample. The biological sample may be derived from another sample.The sample may be a tissue sample, such as a biopsy, core biopsy, needleaspirate, or fine needle aspirate. The sample may be a fluid sample,such as a blood sample, urine sample, or saliva sample. The sample maybe a skin sample. The sample may be a cheek swab. The sample may be aplasma or serum sample. The sample may be a cell-free or cell freesample. A cell-free sample may include extracellular polynucleotides.Extracellular polynucleotides may be isolated from a bodily sample thatmay be selected from the group consisting of blood, plasma, serum,urine, saliva, mucosal excretions, sputum, stool and tears.

The term “biological particle,” as used herein, generally refers to adiscrete biological system derived from a biological sample. Thebiological particle may be a macromolecule. The biological particle maybe a small molecule. The biological particle may be a virus. Thebiological particle may be a cell or derivative of a cell. Thebiological particle may be an organelle. The biological particle may bea rare cell from a population of cells. The biological particle may beany type of cell, including without limitation prokaryotic cells,eukaryotic cells, bacterial, fungal, plant, mammalian, or other animalcell type, mycoplasmas, normal tissue cells, tumor cells, or any othercell type, whether derived from single cell or multicellular organisms.The biological particle may be a constituent of a cell. The biologicalparticle may be or may include DNA, RNA, organelles, proteins,metabolites, or any combination thereof. The biological particle may beor may include a matrix (e.g., a gel or polymer matrix) comprising acell or one or more constituents from a cell (e.g., cell bead), such asDNA, RNA, organelles, proteins, metabolites, or any combination thereof,from the cell. The biological particle may be obtained from a tissue ofa subject. The biological particle may be a hardened cell. Such hardenedcell may or may not include a cell wall or cell membrane. The biologicalparticle may include one or more constituents of a cell, but may notinclude other constituents of the cell. An example of such constituentsis a nucleus or an organelle. A cell may be a live cell. The live cellmay be capable of being cultured, for example, being cultured whenenclosed in a gel or polymer matrix, or cultured when comprising a gelor polymer matrix.

The term “macromolecular constituent,” as used herein, generally refersto a macromolecule contained within or from a biological particle. Themacromolecular constituent may comprise a nucleic acid. In some cases,the biological particle may be a macromolecule. The macromolecularconstituent may comprise DNA. The macromolecular constituent maycomprise RNA. The RNA may be coding or non-coding. The RNA may bemessenger RNA (mRNA), ribosomal RNA (rRNA) or transfer RNA (tRNA), forexample. The RNA may be a transcript. The RNA may be small RNA that areless than 200 nucleic acid bases in length, or large RNA that aregreater than 200 nucleic acid bases in length. Small RNAs may include5.8S ribosomal RNA (rRNA), 5S rRNA, transfer RNA (tRNA), microRNA(miRNA), small interfering RNA (siRNA), small nucleolar RNA (snoRNAs),Piwi-interacting RNA (piRNA), tRNA-derived small RNA (tsRNA) and smallrDNA-derived RNA (srRNA). The RNA may be double-stranded RNA orsingle-stranded RNA. The RNA may be circular RNAThe macromolecularconstituent may comprise a protein. The macromolecular constituent maycomprise a peptide. The macromolecular constituent may comprise apolypeptide.

The term “molecular tag,” as used herein, generally refers to a moleculecapable of binding to a macromolecular constituent. The molecular tagmay bind to the macromolecular constituent with high affinity. Themolecular tag may bind to the macromolecular constituent with highspecificity. The molecular tag may comprise a nucleotide sequence. Themolecular tag may comprise a nucleic acid sequence. The nucleic acidsequence may be at least a portion or an entirety of the molecular tag.The molecular tag may be a nucleic acid molecule or may be part of anucleic acid molecule. The molecular tag may be an oligonucleotide or apolypeptide. The molecular tag may comprise a DNA aptamer. The moleculartag may be or comprise a primer. The molecular tag may be, or comprise,a protein. The molecular tag may comprise a polypeptide. The moleculartag may be a barcode.

The term “partition,” as used herein, generally, refers to a space orvolume that may be suitable to contain one or more species or conductone or more reactions. A partition may be a physical compartment, suchas a droplet or well. The partition may isolate space or volume fromanother space or volume. The droplet may be a first phase (e.g., aqueousphase) in a second phase (e.g., oil) immiscible with the first phase.The droplet may be a first phase in a second phase that does not phaseseparate from the first phase, such as, for example, a capsule orliposome in an aqueous phase. A partition may comprise one or more other(inner) partitions. In some cases, a partition may be a virtualcompartment that can be defined and identified by an index (e.g.,indexed libraries) across multiple and/or remote physical compartments.For example, a physical compartment may comprise a plurality of virtualcompartments.

Provided herein are systems and methods for processing that efficientlyand accurately measure one or more analytes at the single cell level.The systems and methods may identify the cell that the one or moreanalytes originated from. An analyte can be a protein (e.g.,surface-bound protein, internal protein, etc.). An analyte can be ametabolite (e.g., alcohol, amino acid, nucleotide, antioxidant, organicacid, polyol, vitamin, cofactor, etc.). An analyte can be anyconstituent of a cell, such as a small molecule, large molecule, ormacromolecule. An analyte can be a biological particle. The analyte canbe a targeted analyte, such as having binding specificity to an antibodythat is specifically captured and analyzed. The analyte can be anon-targeted analyte that is non-specifically captured and analyzed.

Identification and Measurement of Analytes at the Single Cell Level

A method for identifying a targeted analyte within a cell may comprisegenerating a cell bead from the cell and washing in an antibody into thecell bead. The antibody may have binding specificity to the targetedanalyte and be coupled to a first barcode molecule. The first barcodemolecule may comprise a first barcode sequence. Inside the cell bead,the antibody can bind to or otherwise couple to the targeted analyte,forming an analyte-antibody complex and tagging the targeted analytewith the first barcode sequence. The cell bead may be co-partitionedwith a bead in a partition, wherein the bead is coupled to a secondbarcode molecule. The partition may be a droplet in an emulsion (e.g.,water-in-oil, oil-in-water, etc.). The second barcode molecule maycomprise a second barcode sequence. In the partition, the second barcodemolecule may be released from the bead and attached to theanalyte-antibody complex, thereby tagging the targeted analyte with boththe first barcode sequence and the second barcode sequence. The firstbarcode molecule and the second barcode molecule may form a compositebarcode molecule that comprises a composite sequence comprising thefirst barcode sequence and the second barcode sequence. The firstbarcode sequence may be indicative of the targeted analyte and thesecond barcode sequence may be indicative of the cell. The compositebarcode molecule may be sequenced to identify the targeted analyte andthe cell, and determine that the targeted analyte originated from withinthe cell.

The first barcode molecule may be a nucleic acid molecule, such as anoligonucleotide or polynucleotide. The first barcode sequence mayuniquely identify the type of analyte having binding specificity to theantibody tagged by the first barcode sequence. For example, a firstantibody having binding specificity to a first type of analyte and asecond antibody having binding specificity to a second type of analytecan be tagged with different barcode sequences. A plurality ofantibodies, each having a binding specificity to a same type of analyte(e.g., first type of protein), may each be tagged with the same barcodesequence.

The second barcode molecule may be a nucleic acid molecule, such as anoligonucleotide or polynucleotide. The second barcode sequence mayuniquely identify the bead that the second barcode molecule is coupledthereto. For example, a first bead and a second bead can be coupled tobarcode molecules that comprise different barcode sequences. A pluralityof barcode molecules, each coupled to the same bead, may comprise thesame barcode sequence. A bead, associated with the unique barcodesequence (e.g., the second barcode sequence), may be co-partitioned witha cell. The unique barcode sequence of the bead may be used to uniquelyidentify the cell co-partitioned with the bead.

The composite barcode molecule may be a nucleic acid molecule, such asan oligonucleotide or polynucleotide. The composite barcode sequence maycomprise the first barcode sequence and the second barcode sequence. Insome instances, the composite barcode sequence may comprise one or moreadditional barcode sequences (e.g., unique molecular identifier,anchoring element, etc.) that are described elsewhere herein.

In some instances, the composite barcode molecule may be sequenced todetermine a probability that the targeted analyte originated from withinthe cell. For example, in some instances, two or more beads of aplurality of beads may have the identical barcode sequence (e.g., secondbarcode sequence), which may or may not be intentional. In such cases,identifying the second barcode sequence may be indicative that thetargeted analyte originated from one of two or more cells (eachco-partitioned with a different bead). For example, where five beadshave the identical second barcode sequence, identifying the secondbarcode sequence may be indicative that the targeted analyte originatedfrom one of five cells (each co-partitioned with a different bead). Insome instances, the probability that a targeted analyte originated froma cell may be based at least in part on the probability that thedifferent beads in the system comprise unique second barcode sequences(e.g., if there is substantially a 100% probability that a first beadhas a unique second barcode sequence among a plurality of other beads,identifying the second barcode sequence may be indicative that there issubstantially a 100% probability the targeted analyte originated fromthe cell co-partitioned with the first bead). In some instances, aprobability that the targeted analyte originated from within a cell maybe at least about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 96%,97%, 98%, 99%, or 100%. Alternatively, the probability may be less thanabout 50%.

The targeted analyte can be an internal protein and the antibodycontacting the cell bead may have a binding specificity to the internalprotein. In another example, the targeted analyte can be a metaboliteand the antibody contacting the cell bead may have a binding specificityto the metabolite. In some instances, a metabolite may be an alcohol,amino acid, nucleotide, antioxidant, organic acid, polyol, or vitamin. Ametabolite may be a cofactor. The targeted analyte can be anyconstituent of a cell, such as any small molecule, large molecule, ormacromolecule (e.g., macromolecular constituent). In yet anotherexample, the targeted analyte can be from a class, set, or subset ofanalytes (e.g., proteins, metabolites, small molecules, etc.) sharing astructural similarity or homology (e.g., moiety, functional group,etc.), and the antibody contacting the cell bead may have a bindingspecificity to the class, set, or subset of analytes via the structuralsimilarity. In such cases, the first barcode sequence may uniquelyidentify the class, set, or subset of analytes. Upon binding (orotherwise coupling) to the antibody, the targeted analyte may beclassified by the first barcode sequence as a member of the class, set,or subset of analytes.

Systems and methods for partitioning and using cell beads andbarcode-coupled beads are described in further detail elsewhere herein,such as with reference to FIGS. 1-8.

FIG. 9 illustrates a method for identifying and measuring an analyte ina cell. A cell 902 may be processed to generate a cell bead 904. Thismay be performed by providing the cell 902 in a partition, such as adroplet. Systems and methods for generating a cell bead, such as byencapsulating and polymerizing a cell, are described elsewhere herein.The cell may be lysed to release one or more analytes in the cell bead904, such as a first analyte 906, a second analyte 908, and a thirdanalyte 910. Alternatively, the cell 902 may be lysed prior to formationof the cell bead 904, and a cell bead generated with the lysed contentsthereafter. For example, the cell is provided in a droplet and lysed,and the droplet is subsequently subjected to polymerization to generatethe cell bead 904. A plurality of antibodies may be washed into the cellbead. The plurality of antibodies may comprise a first set of antibodiescomprising a first type of antibody 914 and a second set of antibodiescomprising a second type of antibody 918. The first type of antibody canhave a binding specificity to the first analyte 906 and have coupledthereto a first barcode molecule comprising a first barcode sequence912. The second type of antibody 918 can have a binding specificity tothe second analyte 908 and have coupled thereto a second barcodemolecule comprising a second barcode sequence 916. Antibodies havingbinding specificities to different types of analytes may each have adifferent barcode sequence. A barcode molecule may be a nucleic acidmolecule, such as an oligonucleotide or polynucleotide.

Washed into the cell bead 904, the plurality of antibodies may bind orotherwise couple to one or more analytes in accordance with therespective binding specificity. For example, a first antibody of thefirst type of antibody 914 may bind to (or otherwise couple to) thefirst analyte 906, thereby forming a first analyte-antibody complex 920and tagging the first analyte 906 with the first barcode sequence 912. Asecond antibody of the second type of antibody 918 may bind to (orotherwise couple to) the second analyte 908, thereby forming a secondanalyte-antibody complex 922 and tagging the second analyte 908 with thesecond barcode sequence 916. Unbound antibodies, such as having bindingspecificities to analytes that are not present or those unable to find afree analyte, may be washed out of the cell bead.

Alternative to, or in addition to, washing in a plurality of types ofantibodies in bulk to the cell bead 904, antibodies may be washed intothe cell bead 904 one type at a time (e.g., sequentially). In someinstances, unbound antibodies may be washed out between each washing in.In some instances, unbound antibodies of one or more types may be washedout together.

The cell bead 904 may be co-partitioned with a bead 926 in a partition924. The partition 924 may be a droplet in an emulsion. The bead 926 maybe coupled to a plurality of barcode molecules, each comprising a commonthird barcode sequence 928. For example, FIG. 8 illustrates a beadcoupled to a plurality of barcode molecules. The third barcode sequence928 may be unique to the bead 926. The plurality of barcode moleculesmay be coupled by releasable linkage to the bead 926, as describedelsewhere herein. In the partition 924, the analytes from the cell bead904 may be tagged with the plurality of barcode molecules (e.g., afterrelease from the bead 926).

In some instances, only the analytes bound by (or coupled to) anantibody which is coupled to another barcode molecule (e.g., the firstbarcode molecule coupled to the first type of antibody 914, the secondbarcode molecule coupled to the second type of antibody 916) may betagged by the third barcode sequence 928. For example, the plurality ofbarcode molecules coupled to the bead 926 may comprise a specificpriming sequence that is configured to couple to the another barcodemolecule. Alternatively or in addition, other analytes (e.g., unboundanalytes) may be tagged by the third barcode sequence 928.

An analyte may thus be tagged by a composite barcode sequence, thecomposite barcode sequencing comprising the third barcode sequence 928and another barcode sequence (e.g., the first barcode sequence 912, thesecond barcode sequence 914) tagged by an antibody. For example, thefirst analyte 906 may be tagged by a first composite barcode sequence930 comprising the first barcode sequence 912 and the third barcodesequence 930. The second analyte 908 may be tagged by a second compositebarcode sequence 932 comprising the second barcode sequence 916 and thethird barcode sequence 932. Upon pooling the composite sequences, suchas from different partitions (e.g., comprising different cells andbeads), the composite sequences may be sequenced to measure one or moreanalytes in a cell by attributing the one or more analytes to the cell.

For example, from the first composite barcode sequence 930,identification of the first barcode sequence 912 may be indicative ofthe first type of analyte 906 and identification of the third barcodesequence 928 may be indicative of the cell 904, permitting thedetermination that the first type of analyte 906 originated from thecell 904. In another example, from the second composite barcode sequence932, identification of the second barcode sequence 916 may be indicativeof the second type of analyte 908 and identification of the thirdbarcode sequence 928 may be indicative of the cell 904, permitting thedetermination that the second type of analyte 906 originated from thecell 904. Alternatively or in addition, such as when there is aprobability that two or more beads may share their common barcodesequence (e.g., third barcode sequence 932), identification of the thirdbarcode sequence 928 may be indicative of a probability that aparticular analyte originated from the cell 904. In some cases, therespective probabilities that multiple analytes originated from the cellmay be determined.

While not illustrated in FIG. 9, in other partitions which co-partitiona different cell with a different bead comprising a different commonbarcode sequence, identification of the different common barcodesequence in a composite barcode sequence may be indicative of thedifferent cell, allowing the attribution (e.g., origin, probability oforigin) of one or more analytes to the different cell.

Beneficially, the systems and methods may attribute internal proteins(e.g., not surface-bound) and metabolites to a single cell, and allowfor their accurate and efficient measurement.

Methods of the present disclosure may permit identification of surfacebound and internal analytes (e.g., proteins). For example, withreference to FIG. 9, the cell 902 may be brought in contact with a firstset of antibodies prior to lysing, such as prior to providing the cellin the partition to generate the cell bead 904. In some cases, the cell902 is in a collection of cells that may be brought in contact with thefirst set of antibodies in bulk. Each antibody of the first set ofantibodies may comprise a barcode molecule with a first barcode sequencethat is indicative of surface-bound analytes. In some instances, anantibody in the first set of antibodies may have binding specificity toa given analyte or a given type of analytes. For such instances, in somecases, the barcode molecule on the antibody may comprise additionalbarcode sequence(s) that are selected to be specific for, and indicativeof, the given analyte or the given type of analytes (e.g., type ofprotein). For example, between two antibodies in the first set ofantibodies which each has a binding specificity to a different type ofanalyte, both antibodies may comprise the same first barcode sequence(indicative of surface-bound analytes), but different additionalsequence(s) (indicative of different types of analytes). When the cell902 (prior to lysing) is brought in contact with the first set ofantibodies, the antibodies in the first set of antibodies may couple tosurface-bound analytes (e.g., surface-bound proteins) of the cell 902 toform antibody-analyte complexes, thereby tagging each antibody-bound,surface-bound analyte with the first barcode sequence (indicative ofsurface-bound analytes).

Subsequent to processing the cell 902 with the first set of antibodies,the cell 902 may be used to generate the cell bead 904, as describedabove in the context of FIG. 9. The cell may be lysed prior to or aftergeneration of the cell bead 904. Analytes from within the cell 902 maythen be processed with a second set of antibodies (e.g., antibody 914and antibody 918 used to assay for proteins, metabolites, etc.) bywashing in the second set of antibodies. Each antibody of the second setof antibodies may comprise a barcode molecule with a second barcodesequence that is indicative of internal analytes. In some instances, anantibody in the second set of antibodies may have binding specificity toa given analyte or a given type of analytes. For such instances, in somecases, the barcode molecule on the antibody may comprise additionalbarcode sequence(s) that are selected to be specific for, and indicativeof, the given analyte or the given type of analytes. For example,between two antibodies in the second set of antibodies which each has abinding specificity to a different type of analyte, both antibodies maycomprise the same second barcode sequence (indicative of internalanalytes), but with different additional sequence(s) (indicative ofdifferent types of analytes). When the analytes from within the cell 902are brought in contact with the second set of antibodies, the antibodiesin the second set of antibodies may couple to the internal analytes(from within the cell 902) to form antibody-analyte complexes, therebytagging each antibody-bound, internal analyte with the second barcodesequence (indicative of internal analytes).

In some instances, as described above in the context of FIG. 9, the cellbead (processed by the first set and the second set of antibodies) maybe co-partitioned with a bead comprising a plurality of barcodemolecules comprising a third barcode sequence (indicative of the cell),and each analyte, including surface-bound analytes (tagged by the firstbarcode sequence) and internal analytes (tagged by the second barcodesequence), may be tagged by the third barcode sequence, such as to formcomposite barcode sequences. For example, a first composite sequence maycomprise the first barcode sequence and the third barcode sequence. Inanother example, a second composite sequence may comprise the secondbarcode sequence and the third barcode sequence.

Upon pooling the composite sequences, such as from different partitions(e.g., comprising different cells and beads), the composite sequencesmay be sequenced to measure one or more analytes in a cell byattributing the one or more analytes to the cell. Following sequencing,the first and second barcode sequences may identify surface-bound andinternal analytes, respectively, and the third barcode sequence mayidentify the cell (e.g., 902). In some instances, additional sequence(s)may identify a given analyte or a given type of analyte. Beneficially,the systems and methods of the present disclosure may identify, for ananalyte identified, not only the originating cell, but the originatinglocation (e.g., surface-bound, internal, etc.) in the cell.

Another method for measuring an analyte in a cell may compriseco-partitioning the cell and a bead in a first partition. The firstpartition may be a droplet in an emulsion. The bead may comprise aplurality of antibodies configured to couple to analytes (e.g.,proteins). The plurality of antibodies may be releasably attached to thebead, such as described elsewhere herein. In some instances, a givenantibody of the plurality of antibodies may have non-bindingspecificity, such as to be capable of binding or otherwise coupling todifferent analytes. Alternatively or in addition, a given antibody mayhave binding specificity to a particular type of analyte (e.g., aparticular type of protein). Alternatively or in addition, a givenantibody may have binding specificity to a particular class, set, orsubset of analytes. Each antibody of the plurality of antibodies may becoupled to a common first barcode molecule comprising a common firstbarcode sequence. The common first barcode sequence may be unique to thebead. The cell may be subject to conditions sufficient to permit thegiven antibody to couple with an analyte to generate a firstanalyte-antibody complex, thereby tagging the analyte with the firstbarcode sequence. For example, the cell may be lysed and the antibodiesreleased from the bead.

The first analyte-antibody complex may be pooled with otheranalyte-antibody complexes, such as from the same partition and/ordifferent partitions (e.g., different droplets). The pool ofanalyte-antibody complexes may be sorted by type of analyte in eachanalyte-antibody complex into different partitions. For example, thepartitions may be wells. The first analyte-antibody complex may beco-partitioned in a second partition (e.g., well) along with otheranalyte-antibody complexes of the same type as the firstanalyte-antibody complex, if any. The first analyte-antibody complex maybe co-partitioned with a second barcode molecule comprising a secondbarcode sequence under conditions sufficient to permit the first barcodemolecule of the first analyte-antibody complex and the second barcodemolecule to generate a composite barcode molecule comprising a compositebarcode sequence comprising the first barcode sequence and the secondbarcode sequence, thereby tagging the analyte with both the firstbarcode sequence and the second barcode sequence. The second barcodemolecule may be delivered to the second partition prior to, during, orsubsequent to, partitioning of the first analyte-antibody complex in thesecond partition. The second barcode molecule may be delivered on asupport, such as a bead. The second barcode molecule may be delivered aspart of a plurality of barcode molecules each comprising the secondbarcode sequence. The second barcode sequence may be unique to thesecond partition. Each well (each comprising different types ofanalyte-antibody complexes) may comprise a different barcode sequenceunique to each well. For example, two or more wells comprising the sametype of analyte-antibody complexes may comprise the same common barcodesequence (e.g., the second barcode sequence). The partitions may benon-well partitions.

The composite barcode molecule, or a derivative thereof, may besequenced to identify the cell, from the first barcode sequence in thecomposite barcode sequence, and the analyte, from the second barcodesequence in the composite barcode sequence, and determine that theanalyte originated from the cell.

The first barcode molecule may be a nucleic acid molecule, such as anoligonucleotide or polynucleotide. The first barcode sequence may be anucleic acid sequence. The first barcode sequence may uniquely identifythe bead that the first barcode molecule is coupled thereto. Forexample, a first bead and a second bead can be coupled to barcodemolecules that comprise different barcode sequences. A plurality ofbarcode molecules, each coupled to the same bead, may comprise the samebarcode sequence. A bead, associated with the unique barcode sequence(e.g., the first barcode sequence), may be co-partitioned with a cell.The unique barcode sequence of the bead may be used to uniquely identifythe cell co-partitioned with the bead.

The second barcode molecule may be a nucleic acid molecule, such as anoligonucleotide or polynucleotide. The second barcode sequence mayuniquely identify a partition that the second barcode sequence isdelivered to. For example, different partitions may each be delivereddifferent barcode sequences. The partition may comprise analytes of afirst common type. The unique barcode sequence (e.g., the second barcodesequence) of the partition may be used to uniquely identify the firstcommon type of analytes co-partitioned in the partition. Alternatively,the second barcode sequence may uniquely identify a type of analyte. Forexample, where the first common type of analytes is partitioned in twoor more partitions (e.g., half in a first partition, the other half in asecond partition), the second barcode sequence may be delivered to eachof the two or more partitions, and different unique barcode sequencesmay be delivered to other partitions comprising different types ofanalytes.

The composite barcode molecule may be a nucleic acid molecule, such asan oligonucleotide or polynucleotide. The composite barcode sequence maycomprise the first barcode sequence and the second barcode sequence. Insome instances, the composite barcode sequence may comprise one or moreadditional barcode sequences (e.g., unique molecular identifier,anchoring element, etc.) that are described elsewhere herein.

In some instances, the composite barcode molecule may be sequenced todetermine a probability that the analyte originated from the cell. Forexample, in some instances, two or more beads of a plurality of beadsmay have the identical barcode sequence (e.g., first barcode sequence),which may or may not be intentional. In such cases, identifying thefirst barcode sequence may be indicative that the analyte originatedfrom one of two or more cells (each co-partitioned with a differentbead). For example, where five beads have the identical first barcodesequence, identifying the first barcode sequence may be indicative thatthe analyte originated from one of five cells (each co-partitioned witha different bead). In some instances, the probability that an analyteoriginated from a cell may be based at least in part on the probabilitythat the different beads in the system comprise unique first barcodesequences (e.g., if there is substantially a 100% probability that afirst bead has a unique first barcode sequence among a plurality ofother beads, identifying the first barcode sequence may be indicativethat there is substantially a 100% probability the analyte originatedfrom the cell co-partitioned with the first bead). In some instances, aprobability that the analyte originated from a cell may be at leastabout 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%,99%, or 100%. Alternatively, the probability may be less than about 50%.

The analyte can be an internal protein. In another example, the analytecan be a metabolite. The analyte can be any constituent of a cell, suchas any small molecule, large molecule, or macromolecule (e.g.,macromolecular constituent). In yet another example, the analyte can befrom a class, set, or subset of analytes (e.g., proteins, metabolites,small molecules, etc.) sharing a structural similarity or homology(e.g., moiety, functional group, etc.). The analyte may be a targetedanalyte or from a targeted class of analytes, such as by employingantibodies having binding specificity to the targeted analyte ortargeted class of analytes. The analyte may be a non-targeted analyte.

FIG. 10 illustrates another method for identifying and measuring ananalyte in a cell. A cell 1002 and a bead 1004 may be co-partitioned ina first partition 1006. The first partition 1006 may be a droplet in anemulsion. The bead 1004 may be delivered to the first partition 1006prior to, during, or subsequent to partitioning of the cell 1002 in thefirst partition 1006. Systems and methods for partitioning are describedelsewhere herein. The bead 1004 may be coupled to a plurality ofantibodies 1010, which may or may not have binding specificity to ananalyte or a class of analytes in, or suspected to be in, the cell 1002.Each antibody of the plurality of antibodies 1010 may comprise a commonfirst barcode sequence 1008. The bead 1004 may be coupled to theplurality of antibodies 1010 via one or more barcode molecules (e.g.,comprising the common first barcode sequence 1008). The bead 1004 may bereleasably coupled to the one or more barcode molecules, as describedelsewhere herein. For example, FIG. 8 illustrates a bead coupled to aplurality of barcode molecules. The first barcode sequence 1008 may beunique to the bead 1004.

The cell 1002 may be lysed to release one or more analytes in the firstpartition 1006, such as a first analyte 1012, a second analyte 1014, anda third analyte 1016, each a different type of analyte (e.g., differenttype of protein). The plurality of antibodies 1010 may be released fromthe bead 1004, such as described elsewhere herein (e.g., applying astimulus or stimuli). In the first partition 1006, a given analyte(e.g., 1012, 1014, 1016) from the cell 1002 may bind with (or otherwisecouple to) a given antibody (e.g., 1010) to form a givenanalyte-antibody complex, thereby tagging the given analyte with thefirst barcode sequence 1008. Each analyte-antibody complex formed in thefirst partition 1006 may be tagged with the first barcode sequence 1008,independent of the type of analyte. For example, each of the firstanalyte 1012, second analyte 1014, and the third analyte 1016, which area different type of analyte, may be tagged with the first barcodesequence 1008.

The given analyte-antibody complex may be pooled with otheranalyte-antibody complexes, such as from the same partition (the firstpartition 1006) and/or different partitions (e.g., different droplets).The pool of analyte-antibody complexes may be sorted by type of analytein each analyte-antibody complex into different partitions. For example,the partitions may be wells. For example, a first analyte-antibodycomplex comprising the first analyte 1012 may be partitioned into afirst well along with other analyte-antibody complexes from the firstpartition 1006 or other partitions that comprise the same type ofanalyte as the first analyte 1012. A second analyte-antibody complexcomprising the second analyte 1014 may be partitioned into a second wellalong with other analyte-antibody complexes from the first partition1006 or other partitions that comprise the same type of analyte as thesecond analyte 1014. A third analyte-antibody complex comprising thethird analyte 1016 may be partitioned into a third well along with otheranalyte-antibody complexes from the first partition 1006 or otherpartitions that comprise the same type of analyte as the third analyte1016.

In FIG. 10, for example, the first well comprises the firstanalyte-antibody complex from the first partition 1006, and anotheranalyte-antibody complex of the same type as the first analyte 1012 froma first other partition which co-partitioned a second cell and a secondbead comprising a second barcode sequence 1018, thereby tagged with thesecond barcode sequence 1018. The second well comprises the secondanalyte-antibody complex from the first partition 1006, and anotheranalyte-antibody complex of the same type as the second analyte 1014from the first other partition, thereby tagged with the second barcodesequence 1018, and another analyte-antibody complex of the same type asthe second analyte 1014 from a second other partition whichco-partitioned a third cell and a third bead comprising a third barcodesequence 1020, thereby tagged with the third barcode sequence 1020. Thethird well comprises the third analyte-antibody complex from the firstpartition 1006.

In some instances, a type of analyte may be sorted into more than onewell. For example, a plurality of analyte-antibody complexes eachcomprising the same first type of analyte may be distributed across twoor more wells, provided that each well comprises only one type ofanalyte.

A barcode molecule comprising a barcode sequence unique to each well maybe delivered to each well. For example, a barcode molecule comprising afourth barcode sequence 1022 may be delivered to the first well, abarcode molecule comprising a fifth barcode sequence 1024 may bedelivered to the second well, and a barcode molecule comprising a sixthbarcode sequence 1026 may be delivered to the third well. In someinstances, the barcode molecule may be delivered via a bead to eachwell. In some instances, the barcode molecule may be delivered as partof a plurality of barcode molecules that each comprises the same uniquebarcode sequence. For example, the fourth barcode sequence 1022 may beunique to the first well, the fifth barcode sequence 1024 may be uniqueto the second well, and the sixth barcode sequence 1026 may be unique tothe third well.

Alternatively or in addition to, a barcode molecule comprising a barcodesequence unique to a type of analyte may be delivered to each well. Forexample, where two or more wells comprise the same type of analyte, thesame barcode sequence may be delivered to the two or more wells.

The wells and their constituents may be subject to conditions sufficientto permit the given barcode molecule (e.g., comprising 1022, 1024, 1026)delivered to the wells and a given barcode molecule of theanalyte-antibody complexes to generate a given composite barcodemolecule comprising a composite barcode sequence. The composite barcodesequence may comprise the barcode sequence of the barcode moleculedelivered to the well and the barcode sequence tagged on theanalyte-antibody complex.

For example, in FIG. 10, in the first well, a first composite barcodesequence comprises the first barcode sequence 1008 from the firstpartition 1006 (unique to the first partition) and the fourth barcodesequence 1022 (unique to the first well), and a second composite barcodesequence comprises the second barcode sequence 1018 from the first otherpartition (unique to the first other partition) and the fourth barcodesequence 1022 (unique to the first well). In the second well, a thirdcomposite barcode sequence comprises the first barcode sequence 1008from the first partition 1006 (unique to the first partition) and thefifth barcode sequence 1024 (unique to the second well), a fourthcomposite barcode sequence comprises the second barcode sequence 1018from the first other partition (unique to the first other partition) andthe fifth barcode sequence 1022 (unique to the second well), and a fifthcomposite barcode sequence comprises the third barcode sequence 1020from the second other partition (unique to the second other partition)and the fifth barcode sequence 1022 (unique to the second well). In thethird well, a sixth composite barcode sequence comprises the firstbarcode sequence 1008 from the first partition 1006 (unique to the firstpartition) and the sixth barcode sequence 1026 (unique to the thirdwell).

Upon pooling the composite sequences, such as from different partitions(e.g., wells), the composite sequences may be sequenced to measure oneor more analytes in a cell by attributing the one or more analytes tothe cell.

For example, from the first composite barcode sequence, identificationof the first barcode sequence 1008 may be indicative of the cell 1002and identification of the fourth barcode sequence 1022 may be indicativeof the first analyte 1012 type, permitting the determination that thefirst analyte 1012 type originated from the cell 1002. In anotherexample, from the fifth composite barcode sequence, identification ofthe third barcode sequence 1020 may be indicative of the third cell(co-partitioned with the third bead comprising the third barcodesequence 1020 in the second other partition) and identification of thefifth barcode sequence 1022 may be indicative of the second analyte 1014type, permitting the determination that the second analyte 1014 typeoriginated from the second cell. Alternatively or in addition, such aswhen there is a probability that two or more beads may share theircommon barcode sequence (e.g., first barcode sequence 1008),identification of the first barcode sequence 1008 may be indicative of aprobability that a particular type of analyte originated from the cell1004. Respective probabilities for different types of analytes may bedetermined.

While FIG. 10 illustrates the identification of three different types ofanalytes, there may be any number of analytes identified. While FIG. 10illustrates the identification of three different types of cells, theremay be any number of cells identified.

While the systems and methods described in relation to FIGS. 9 and 10illustrate the capture of one or more analytes via the use of one ormore antibodies, which may or may not have binding specificity, thesystems and methods may be applied using other adaptors or molecules(e.g., peptides) configured to couple to one or more analytes, such asspecific priming sequences or random primers. For example, with respectto FIG. 10, the bead may be coupled to a plurality of adaptors ormolecules configured to couple to one or more analytes. In someinstances, the bead may be coupled to one or more populations ofdifferent adaptors or molecules comprising barcode sequences, such as afirst population of antibodies and a second population of primingsequences.

Methods of the present disclosure may be used to identify informationabout analytes from a cell, including identity (e.g., type) of ananalyte and location (e.g., surface-bound, internal) of the analyte.Such analytes may include, for example, proteins, metabolites,ribonucleic acid (RNA) molecules, and deoxyribonucleic acid (DNA)molecules. In some examples, proteomic information may be obtained forthe cell and combined with genomic (e.g., DNA or genomic variants)and/or transcriptomic (e.g., mRNA) information about the cell. This maypermit identifying, for example, genes that are transcribed into mRNAand mRNA that is translated to protein.

A computer system, for example, described with respect to FIG. 11, maybe used to implement the systems and methods of the present disclosure,such as to generate and maintain one or more libraries, as well asperform sequencing, and analyze the results of such sequencing toidentify one or more analytes, identify one or more cells, and/orattribute an identified analyte to an identified cell. Beneficially, thesystems and methods provided herein may efficiently and accuratelymeasure one or more analytes at the single cell level.

Systems and Methods for Sample Compartmentalization

In an aspect, the systems and methods described herein provide for thecompartmentalization, depositing, or partitioning of one or moreparticles (e.g., biological particles, macromolecular constituents ofbiological particles, beads, reagents, etc.) into discrete compartmentsor partitions (referred to interchangeably herein as partitions), whereeach partition maintains separation of its own contents from thecontents of other partitions. The partition can be a droplet in anemulsion. A partition may comprise one or more other partitions.

A partition may include one or more particles. A partition may includeone or more types of particles. For example, s partition of the presentdisclosure may comprise one or more biological particles and/ormacromolecular constituents thereof. A partition may comprise one ormore gel beads. A partition may comprise one or more cell beads. Apartition may include a single gel bead, a single cell bead, or both asingle cell bead and single gel bead. A partition may include one ormore reagents. Alternatively, a partition may be unoccupied. Forexample, a partition may not comprise a bead. A cell bead can be abiological particle and/or one or more of its macromolecularconstituents encased inside of a gel or polymer matrix, such as viapolymerization of a droplet containing the biological particle andprecursors capable of being polymerized or gelled. Unique identifiers,such as barcodes, may be injected into the droplets previous to,subsequent to, or concurrently with droplet generation, such as via amicrocapsule (e.g., bead), as described elsewhere herein. Microfluidicchannel networks (e.g., on a chip) can be utilized to generatepartitions as described herein. Alternative mechanisms may also beemployed in the partitioning of individual biological particles,including porous membranes through which aqueous mixtures of cells areextruded into non-aqueous fluids.

The partitions can be flowable within fluid streams. The partitions maycomprise, for example, micro-vesicles that have an outer barriersurrounding an inner fluid center or core. In some cases, the partitionsmay comprise a porous matrix that is capable of entraining and/orretaining materials within its matrix. The partitions can be droplets ofa first phase within a second phase, wherein the first and second phasesare immiscible. For example, the partitions can be droplets of aqueousfluid within a non-aqueous continuous phase (e.g., oil phase). Inanother example, the partitions can be droplets of a non-aqueous fluidwithin an aqueous phase. In some examples, the partitions may beprovided in a water-in-oil emulsion or oil-in-water emulsion. A varietyof different vessels are described in, for example, U.S. PatentApplication Publication No. 2014/0155295, which is entirely incorporatedherein by reference for all purposes. Emulsion systems for creatingstable droplets in non-aqueous or oil continuous phases are describedin, for example, U.S. Patent Application Publication No. 2010/0105112,which is entirely incorporated herein by reference for all purposes.

In the case of droplets in an emulsion, allocating individual particlesto discrete partitions may in one non-limiting example be accomplishedby introducing a flowing stream of particles in an aqueous fluid into aflowing stream of a non-aqueous fluid, such that droplets are generatedat the junction of the two streams. Fluid properties (e.g., fluid flowrates, fluid viscosities, etc.), particle properties (e.g., volumefraction, particle size, particle concentration, etc.), microfluidicarchitectures (e.g., channel geometry, etc.), and other parameters maybe adjusted to control the occupancy of the resulting partitions (e.g.,number of biological particles per partition, number of beads perpartition, etc.). For example, partition occupancy can be controlled byproviding the aqueous stream at a certain concentration and/or flow rateof particles. To generate single biological particle partitions, therelative flow rates of the immiscible fluids can be selected such that,on average, the partitions may contain less than one biological particleper partition in order to ensure that those partitions that are occupiedare primarily singly occupied. In some cases, partitions among aplurality of partitions may contain at most one biological particle(e.g., bead, DNA, cell or cellular material). In some embodiments, thevarious parameters (e.g., fluid properties, particle properties,microfluidic architectures, etc.) may be selected or adjusted such thata majority of partitions are occupied, for example, allowing for only asmall percentage of unoccupied partitions. The flows and channelarchitectures can be controlled as to ensure a given number of singlyoccupied partitions, less than a certain level of unoccupied partitionsand/or less than a certain level of multiply occupied partitions.

FIG. 1 shows an example of a microfluidic channel structure 100 forpartitioning individual biological particles. The channel structure 100can include channel segments 102, 104, 106 and 108 communicating at achannel junction 110. In operation, a first aqueous fluid 112 thatincludes suspended biological particles (or cells) 114 may betransported along channel segment 102 into junction 110, while a secondfluid 116 that is immiscible with the aqueous fluid 112 is delivered tothe junction 110 from each of channel segments 104 and 106 to creatediscrete droplets 118, 120 of the first aqueous fluid 112 flowing intochannel segment 108, and flowing away from junction 110. The channelsegment 108 may be fluidically coupled to an outlet reservoir where thediscrete droplets can be stored and/or harvested. A discrete dropletgenerated may include an individual biological particle 114 (such asdroplets 118). A discrete droplet generated may include more than oneindividual biological particle 114 (not shown in FIG. 1). A discretedroplet may contain no biological particle 114 (such as droplet 120).Each discrete partition may maintain separation of its own contents(e.g., individual biological particle 114) from the contents of otherpartitions.

The second fluid 116 can comprise an oil, such as a fluorinated oil,that includes a fluorosurfactant for stabilizing the resulting droplets,for example, inhibiting subsequent coalescence of the resulting droplets118, 120. Examples of particularly useful partitioning fluids andfluorosurfactants are described, for example, in U.S. Patent ApplicationPublication No. 2010/0105112, which is entirely incorporated herein byreference for all purposes.

As will be appreciated, the channel segments described herein may becoupled to any of a variety of different fluid sources or receivingcomponents, including reservoirs, tubing, manifolds, or fluidiccomponents of other systems. As will be appreciated, the microfluidicchannel structure 100 may have other geometries. For example, amicrofluidic channel structure can have more than one channel junction.For example, a microfluidic channel structure can have 2, 3, 4, or 5channel segments each carrying particles (e.g., biological particles,cell beads, and/or gel beads) that meet at a channel junction. Fluid maybe directed to flow along one or more channels or reservoirs via one ormore fluid flow units. A fluid flow unit can comprise compressors (e.g.,providing positive pressure), pumps (e.g., providing negative pressure),actuators, and the like to control flow of the fluid. Fluid may also orotherwise be controlled via applied pressure differentials, centrifugalforce, electrokinetic pumping, vacuum, capillary or gravity flow, or thelike.

The generated droplets may comprise two subsets of droplets: (1)occupied droplets 118, containing one or more biological particles 114,and (2) unoccupied droplets 120, not containing any biological particles114. Occupied droplets 118 may comprise singly occupied droplets (havingone biological particle) and multiply occupied droplets (having morethan one biological particle). As described elsewhere herein, in somecases, the majority of occupied partitions can include no more than onebiological particle per occupied partition and some of the generatedpartitions can be unoccupied (of any biological particle). In somecases, though, some of the occupied partitions may include more than onebiological particle. In some cases, the partitioning process may becontrolled such that fewer than about 25% of the occupied partitionscontain more than one biological particle, and in many cases, fewer thanabout 20% of the occupied partitions have more than one biologicalparticle, while in some cases, fewer than about 10% or even fewer thanabout 5% of the occupied partitions include more than one biologicalparticle per partition.

In some cases, it may be desirable to minimize the creation of excessivenumbers of empty partitions, such as to reduce costs and/or increaseefficiency. While this minimization may be achieved by providing asufficient number of biological particles (e.g., biological particles114) at the partitioning junction 110, such as to ensure that at leastone biological particle is encapsulated in a partition, the Poissoniandistribution may expectedly increase the number of partitions thatinclude multiple biological particles. As such, where singly occupiedpartitions are to be obtained, at most about 95%, 90%, 85%, 80%, 75%,70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5% orless of the generated partitions can be unoccupied.

In some cases, the flow of one or more of the biological particles(e.g., in channel segment 102), or other fluids directed into thepartitioning junction (e.g., in channel segments 104, 106) can becontrolled such that, in many cases, no more than about 50% of thegenerated partitions, no more than about 25% of the generatedpartitions, or no more than about 10% of the generated partitions areunoccupied. These flows can be controlled so as to present anon-Poissonian distribution of single-occupied partitions whileproviding lower levels of unoccupied partitions. The above noted rangesof unoccupied partitions can be achieved while still providing any ofthe single occupancy rates described above. For example, in many cases,the use of the systems and methods described herein can create resultingpartitions that have multiple occupancy rates of less than about 25%,less than about 20%, less than about 15%, less than about 10%, and inmany cases, less than about 5%, while having unoccupied partitions ofless than about 50%, less than about 40%, less than about 30%, less thanabout 20%, less than about 10%, less than about 5%, or less.

As will be appreciated, the above-described occupancy rates are alsoapplicable to partitions that include both biological particles andadditional reagents, including, but not limited to, microcapsules orbeads (e.g., gel beads) carrying barcoded nucleic acid molecules (e.g.,oligonucleotides) (described in relation to FIG. 2). The occupiedpartitions (e.g., at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%,90%, 95%, or 99% of the occupied partitions) can include both amicrocapsule (e.g., bead) comprising barcoded nucleic acid molecules anda biological particle.

In another aspect, in addition to or as an alternative to droplet basedpartitioning, biological particles may be encapsulated within amicrocapsule that comprises an outer shell, layer or porous matrix inwhich is entrained one or more individual biological particles or smallgroups of biological particles. The microcapsule may include otherreagents. Encapsulation of biological particles may be performed by avariety of processes. Such processes may combine an aqueous fluidcontaining the biological particles with a polymeric precursor materialthat may be capable of being formed into a gel or other solid orsemi-solid matrix upon application of a particular stimulus to thepolymer precursor. Such stimuli can include, for example, thermalstimuli (e.g., either heating or cooling), photo-stimuli (e.g., throughphoto-curing), chemical stimuli (e.g., through crosslinking,polymerization initiation of the precursor (e.g., through addedinitiators)), mechanical stimuli, or a combination thereof.

Preparation of microcapsules comprising biological particles may beperformed by a variety of methods. For example, air knife droplet oraerosol generators may be used to dispense droplets of precursor fluidsinto gelling solutions in order to form microcapsules that includeindividual biological particles or small groups of biological particles.Likewise, membrane based encapsulation systems may be used to generatemicrocapsules comprising encapsulated biological particles as describedherein. Microfluidic systems of the present disclosure, such as thatshown in FIG. 1, may be readily used in encapsulating cells as describedherein. In particular, and with reference to FIG. 1, the aqueous fluid112 comprising (i) the biological particles 114 and (ii) the polymerprecursor material (not shown) is flowed into channel junction 110,where it is partitioned into droplets 118, 120 through the flow ofnon-aqueous fluid 116. In the case of encapsulation methods, non-aqueousfluid 116 may also include an initiator (not shown) to causepolymerization and/or crosslinking of the polymer precursor to form themicrocapsule that includes the entrained biological particles. Examplesof polymer precursor/initiator pairs include those described in U.S.Patent Application Publication No. 2014/0378345, which is entirelyincorporated herein by reference for all purposes.

For example, in the case where the polymer precursor material comprisesa linear polymer material, such as a linear polyacrylamide, PEG, orother linear polymeric material, the activation agent may comprise across-linking agent, or a chemical that activates a cross-linking agentwithin the formed droplets. Likewise, for polymer precursors thatcomprise polymerizable monomers, the activation agent may comprise apolymerization initiator. For example, in certain cases, where thepolymer precursor comprises a mixture of acrylamide monomer with aN,N′-bis-(acryloyl)cystamine (BAC) comonomer, an agent such astetraethylmethylenediamine (TEMED) may be provided within the secondfluid streams 116 in channel segments 104 and 106, which can initiatethe copolymerization of the acrylamide and BAC into a cross-linkedpolymer network, or hydrogel.

Upon contact of the second fluid stream 116 with the first fluid stream112 at junction 110, during formation of droplets, the TEMED may diffusefrom the second fluid 116 into the aqueous fluid 112 comprising thelinear polyacrylamide, which will activate the crosslinking of thepolyacrylamide within the droplets 118, 120, resulting in the formationof gel (e.g., hydrogel) microcapsules, as solid or semi-solid beads orparticles entraining the cells 114. Although described in terms ofpolyacrylamide encapsulation, other ‘activatable’ encapsulationcompositions may also be employed in the context of the methods andcompositions described herein. For example, formation of alginatedroplets followed by exposure to divalent metal ions (e.g., Ca²⁺ ions),can be used as an encapsulation process using the described processes.Likewise, agarose droplets may also be transformed into capsules throughtemperature based gelling (e.g., upon cooling, etc.).

In some cases, encapsulated biological particles can be selectivelyreleasable from the microcapsule, such as through passage of time orupon application of a particular stimulus, that degrades themicrocapsule sufficiently to allow the biological particles (e.g.,cell), or its other contents to be released from the microcapsule, suchas into a partition (e.g., droplet). For example, in the case of thepolyacrylamide polymer described above, degradation of the microcapsulemay be accomplished through the introduction of an appropriate reducingagent, such as DTT or the like, to cleave disulfide bonds thatcross-link the polymer matrix. See, for example, U.S. Patent ApplicationPublication No. 2014/0378345, which is entirely incorporated herein byreference for all purposes.

The biological particle can be subjected to other conditions sufficientto polymerize or gel the precursors. The conditions sufficient topolymerize or gel the precursors may comprise exposure to heating,cooling, electromagnetic radiation, and/or light. The conditionssufficient to polymerize or gel the precursors may comprise anyconditions sufficient to polymerize or gel the precursors. Followingpolymerization or gelling, a polymer or gel may be formed around thebiological particle. The polymer or gel may be diffusively permeable tochemical or biochemical reagents. The polymer or gel may be diffusivelyimpermeable to macromolecular constituents of the biological particle.In this manner, the polymer or gel may act to allow the biologicalparticle to be subjected to chemical or biochemical operations whilespatially confining the macromolecular constituents to a region of thedroplet defined by the polymer or gel. The polymer or gel may includeone or more of disulfide cross-linked polyacrylamide, agarose, alginate,polyvinyl alcohol, polyethylene glycol (PEG)-diacrylate, PEG-acrylate,PEG-thiol, PEG-azide, PEG-alkyne, other acrylates, chitosan, hyaluronicacid, collagen, fibrin, gelatin, or elastin. The polymer or gel maycomprise any other polymer or gel.

The polymer or gel may be functionalized to bind to targeted analytes,such as nucleic acids, proteins, carbohydrates, lipids or otheranalytes. The polymer or gel may be polymerized or gelled via a passivemechanism. The polymer or gel may be stable in alkaline conditions or atelevated temperature. The polymer or gel may have mechanical propertiessimilar to the mechanical properties of the bead. For instance, thepolymer or gel may be of a similar size to the bead. The polymer or gelmay have a mechanical strength (e.g. tensile strength) similar to thatof the bead. The polymer or gel may be of a lower density than an oil.The polymer or gel may be of a density that is roughly similar to thatof a buffer. The polymer or gel may have a tunable pore size. The poresize may be chosen to, for instance, retain denatured nucleic acids. Thepore size may be chosen to maintain diffusive permeability to exogenouschemicals such as sodium hydroxide (NaOH) and/or endogenous chemicalssuch as inhibitors. The polymer or gel may be biocompatible. The polymeror gel may maintain or enhance cell viability. The polymer or gel may bebiochemically compatible. The polymer or gel may be polymerized and/ordepolymerized thermally, chemically, enzymatically, and/or optically.

The polymer may comprise poly(acrylamide-co-acrylic acid) crosslinkedwith disulfide linkages. The preparation of the polymer may comprise atwo-step reaction. In the first activation step,poly(acrylamide-co-acrylic acid) may be exposed to an acylating agent toconvert carboxylic acids to esters. For instance, thepoly(acrylamide-co-acrylic acid) may be exposed to4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride(DMTMM). The polyacrylamide-co-acrylic acid may be exposed to othersalts of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium. Inthe second cross-linking step, the ester formed in the first step may beexposed to a disulfide crosslinking agent. For instance, the ester maybe exposed to cystamine (2,2′-dithiobis(ethylamine)). Following the twosteps, the biological particle may be surrounded by polyacrylamidestrands linked together by disulfide bridges. In this manner, thebiological particle may be encased inside of or comprise a gel or matrix(e.g., polymer matrix) to form a “cell bead.” A cell bead can containbiological particles (e.g., a cell) or macromolecular constituents(e.g., RNA, DNA, proteins, etc.) of biological particles. A cell beadmay include a single cell or multiple cells, or a derivative of thesingle cell or multiple cells. For example after lysing and washing thecells, inhibitory components from cell lysates can be washed away andthe macromolecular constituents can be bound as cell beads. Systems andmethods disclosed herein can be applicable to both cell beads (and/ordroplets or other partitions) containing biological particles and cellbeads (and/or droplets or other partitions) containing macromolecularconstituents of biological particles.

Encapsulated biological particles can provide certain potentialadvantages of being more storable and more portable than droplet-basedpartitioned biological particles. Furthermore, in some cases, it may bedesirable to allow biological particles to incubate for a select periodof time before analysis, such as in order to characterize changes insuch biological particles over time, either in the presence or absenceof different stimuli. In such cases, encapsulation may allow for longerincubation than partitioning in emulsion droplets, although in somecases, droplet partitioned biological particles may also be incubatedfor different periods of time, e.g., at least 10 seconds, at least 30seconds, at least 1 minute, at least 5 minutes, at least 10 minutes, atleast 30 minutes, at least 1 hour, at least 2 hours, at least 5 hours,or at least 10 hours or more. The encapsulation of biological particlesmay constitute the partitioning of the biological particles into whichother reagents are co-partitioned. Alternatively or in addition,encapsulated biological particles may be readily deposited into otherpartitions (e.g., droplets) as described above.

Beads

A partition may comprise one or more unique identifiers, such asbarcodes. Barcodes may be previously, subsequently or concurrentlydelivered to the partitions that hold the compartmentalized orpartitioned biological particle. For example, barcodes may be injectedinto droplets previous to, subsequent to, or concurrently with dropletgeneration. The delivery of the barcodes to a particular partitionallows for the later attribution of the characteristics of theindividual biological particle to the particular partition. Barcodes maybe delivered, for example on a nucleic acid molecule (e.g., anoligonucleotide), to a partition via any suitable mechanism. Barcodednucleic acid molecules can be delivered to a partition via amicrocapsule. A microcapsule, in some instances, can comprise a bead.Beads are described in further detail below.

In some cases, barcoded nucleic acid molecules can be initiallyassociated with the microcapsule and then released from themicrocapsule. Release of the barcoded nucleic acid molecules can bepassive (e.g., by diffusion out of the microcapsule). In addition oralternatively, release from the microcapsule can be upon application ofa stimulus which allows the barcoded nucleic acid nucleic acid moleculesto dissociate or to be released from the microcapsule. Such stimulus maydisrupt the microcapsule, an interaction that couples the barcodednucleic acid molecules to or within the microcapsule, or both. Suchstimulus can include, for example, a thermal stimulus, photo-stimulus,chemical stimulus (e.g., change in pH or use of a reducing agent(s)), amechanical stimulus, a radiation stimulus; a biological stimulus (e.g.,enzyme), or any combination thereof.

FIG. 2 shows an example of a microfluidic channel structure 200 fordelivering barcode carrying beads to droplets. The channel structure 200can include channel segments 201, 202, 204, 206 and 208 communicating ata channel junction 210. In operation, the channel segment 201 maytransport an aqueous fluid 212 that includes a plurality of beads 214(e.g., with nucleic acid molecules, oligonucleotides, molecular tags)along the channel segment 201 into junction 210. The plurality of beads214 may be sourced from a suspension of beads. For example, the channelsegment 201 may be connected to a reservoir comprising an aqueoussuspension of beads 214. The channel segment 202 may transport theaqueous fluid 212 that includes a plurality of biological particles 216along the channel segment 202 into junction 210. The plurality ofbiological particles 216 may be sourced from a suspension of biologicalparticles. For example, the channel segment 202 may be connected to areservoir comprising an aqueous suspension of biological particles 216.In some instances, the aqueous fluid 212 in either the first channelsegment 201 or the second channel segment 202, or in both segments, caninclude one or more reagents, as further described below. A second fluid218 that is immiscible with the aqueous fluid 212 (e.g., oil) can bedelivered to the junction 210 from each of channel segments 204 and 206.Upon meeting of the aqueous fluid 212 from each of channel segments 201and 202 and the second fluid 218 from each of channel segments 204 and206 at the channel junction 210, the aqueous fluid 212 can bepartitioned as discrete droplets 220 in the second fluid 218 and flowaway from the junction 210 along channel segment 208. The channelsegment 208 may deliver the discrete droplets to an outlet reservoirfluidly coupled to the channel segment 208, where they may be harvested.

As an alternative, the channel segments 201 and 202 may meet at anotherjunction upstream of the junction 210. At such junction, beads andbiological particles may form a mixture that is directed along anotherchannel to the junction 210 to yield droplets 220. The mixture mayprovide the beads and biological particles in an alternating fashion,such that, for example, a droplet comprises a single bead and a singlebiological particle.

Beads, biological particles and droplets may flow along channels atsubstantially regular flow profiles (e.g., at regular flow rates). Suchregular flow profiles may permit a droplet to include a single bead anda single biological particle. Such regular flow profiles may permit thedroplets to have an occupancy (e.g., droplets having beads andbiological particles) greater than 5%, 10%, 20%, 30%, 40%, 50%, 60%,70%, 80%, 90%, or 95%. Such regular flow profiles and devices that maybe used to provide such regular flow profiles are provided in, forexample, U.S. Patent Publication No. 2015/0292988, which is entirelyincorporated herein by reference.

The second fluid 218 can comprise an oil, such as a fluorinated oil,that includes a fluorosurfactant for stabilizing the resulting droplets,for example, inhibiting subsequent coalescence of the resulting droplets220.

A discrete droplet that is generated may include an individualbiological particle 216. A discrete droplet that is generated mayinclude a barcode or other reagent carrying bead 214. A discrete dropletgenerated may include both an individual biological particle and abarcode carrying bead, such as droplets 220. In some instances, adiscrete droplet may include more than one individual biologicalparticle or no biological particle. In some instances, a discretedroplet may include more than one bead or no bead. A discrete dropletmay be unoccupied (e.g., no beads, no biological particles).

Beneficially, a discrete droplet partitioning a biological particle anda barcode carrying bead may effectively allow the attribution of thebarcode to macromolecular constituents of the biological particle withinthe partition. The contents of a partition may remain discrete from thecontents of other partitions.

As will be appreciated, the channel segments described herein may becoupled to any of a variety of different fluid sources or receivingcomponents, including reservoirs, tubing, manifolds, or fluidiccomponents of other systems. As will be appreciated, the microfluidicchannel structure 200 may have other geometries. For example, amicrofluidic channel structure can have more than one channel junctions.For example, a microfluidic channel structure can have 2, 3, 4, or 5channel segments each carrying beads that meet at a channel junction.Fluid may be directed flow along one or more channels or reservoirs viaone or more fluid flow units. A fluid flow unit can comprise compressors(e.g., providing positive pressure), pumps (e.g., providing negativepressure), actuators, and the like to control flow of the fluid. Fluidmay also or otherwise be controlled via applied pressure differentials,centrifugal force, electrokinetic pumping, vacuum, capillary or gravityflow, or the like.

A bead may be porous, non-porous, solid, semi-solid, semi-fluidic,fluidic, and/or a combination thereof. In some instances, a bead may bedissolvable, disruptable, and/or degradable. In some cases, a bead maynot be degradable. In some cases, the bead may be a gel bead. A gel beadmay be a hydrogel bead. A gel bead may be formed from molecularprecursors, such as a polymeric or monomeric species. A semi-solid beadmay be a liposomal bead. Solid beads may comprise metals including ironoxide, gold, and silver. In some cases, the bead may be a silica bead.In some cases, the bead can be rigid. In other cases, the bead may beflexible and/or compressible.

A bead may be of any suitable shape. Examples of bead shapes include,but are not limited to, spherical, non-spherical, oval, oblong,amorphous, circular, cylindrical, and variations thereof.

Beads may be of uniform size or heterogeneous size. In some cases, thediameter of a bead may be at least about 10 nanometers (nm), 100 nm, 500nm, 1 micrometer (μm), 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm,70 μm, 80 μm, 90 μm, 100 μm, 250 μm, 500 μm, 1 mm, or greater. In somecases, a bead may have a diameter of less than about 10 nm, 100 nm, 500nm, lμm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm,90 μm, 100 μm, 250 μm, 500 μm, 1 mm, or less. In some cases, a bead mayhave a diameter in the range of about 40-75 μm, 30-75 μm, 20-75 μm,40-85 μm, 40-95 μm, 20-100 μm, 10-100 μm, 1-100 μm, 20-250 m, or 20-500m.

In certain aspects, beads can be provided as a population or pluralityof beads having a relatively monodisperse size distribution. Where itmay be desirable to provide relatively consistent amounts of reagentswithin partitions, maintaining relatively consistent beadcharacteristics, such as size, can contribute to the overallconsistency. In particular, the beads described herein may have sizedistributions that have a coefficient of variation in theircross-sectional dimensions of less than 50%, less than 40%, less than30%, less than 20%, and in some cases less than 15%, less than 10%, lessthan 5%, or less.

A bead may comprise natural and/or synthetic materials. For example, abead can comprise a natural polymer, a synthetic polymer or both naturaland synthetic polymers. Examples of natural polymers include proteinsand sugars such as deoxyribonucleic acid, rubber, cellulose, starch(e.g., amylose, amylopectin), proteins, enzymes, polysaccharides, silks,polyhydroxyalkanoates, chitosan, dextran, collagen, carrageenan,ispaghula, acacia, agar, gelatin, shellac, sterculia gum, xanthan gum,Corn sugar gum, guar gum, gum karaya, agarose, alginic acid, alginate,or natural polymers thereof. Examples of synthetic polymers includeacrylics, nylons, silicones, spandex, viscose rayon, polycarboxylicacids, polyvinyl acetate, polyacrylamide, polyacrylate, polyethyleneglycol, polyurethanes, polylactic acid, silica, polystyrene,polyacrylonitrile, polybutadiene, polycarbonate, polyethylene,polyethylene terephthalate, poly(chlorotrifluoroethylene), poly(ethyleneoxide), poly(ethylene terephthalate), polyethylene, polyisobutylene,poly(methyl methacrylate), poly(oxymethylene), polyformaldehyde,polypropylene, polystyrene, poly(tetrafluoroethylene), poly(vinylacetate), poly(vinyl alcohol), poly(vinyl chloride), poly(vinylidenedichloride), poly(vinylidene difluoride), poly(vinyl fluoride) and/orcombinations (e.g., co-polymers) thereof. Beads may also be formed frommaterials other than polymers, including lipids, micelles, ceramics,glass-ceramics, material composites, metals, other inorganic materials,and others.

In some instances, the bead may contain molecular precursors (e.g.,monomers or polymers), which may form a polymer network viapolymerization of the molecular precursors. In some cases, a precursormay be an already polymerized species capable of undergoing furtherpolymerization via, for example, a chemical cross-linkage. In somecases, a precursor can comprise one or more of an acrylamide or amethacrylamide monomer, oligomer, or polymer. In some cases, the beadmay comprise prepolymers, which are oligomers capable of furtherpolymerization. For example, polyurethane beads may be prepared usingprepolymers. In some cases, the bead may contain individual polymersthat may be further polymerized together. In some cases, beads may begenerated via polymerization of different precursors, such that theycomprise mixed polymers, co-polymers, and/or block co-polymers. In somecases, the bead may comprise covalent or ionic bonds between polymericprecursors (e.g., monomers, oligomers, linear polymers), nucleic acidmolecules (e.g., oligonucleotides), primers, and other entities. In somecases, the covalent bonds can be carbon-carbon bonds, thioether bonds,or carbon-heteroatom bonds.

Cross-linking may be permanent or reversible, depending upon theparticular cross-linker used. Reversible cross-linking may allow for thepolymer to linearize or dissociate under appropriate conditions. In somecases, reversible cross-linking may also allow for reversible attachmentof a material bound to the surface of a bead. In some cases, across-linker may form disulfide linkages. In some cases, the chemicalcross-linker forming disulfide linkages may be cystamine or a modifiedcystamine.

In some cases, disulfide linkages can be formed between molecularprecursor units (e.g., monomers, oligomers, or linear polymers) orprecursors incorporated into a bead and nucleic acid molecules (e.g.,oligonucleotides). Cystamine (including modified cystamines), forexample, is an organic agent comprising a disulfide bond that may beused as a crosslinker agent between individual monomeric or polymericprecursors of a bead. Polyacrylamide may be polymerized in the presenceof cystamine or a species comprising cystamine (e.g., a modifiedcystamine) to generate polyacrylamide gel beads comprising disulfidelinkages (e.g., chemically degradable beads comprisingchemically-reducible cross-linkers). The disulfide linkages may permitthe bead to be degraded (or dissolved) upon exposure of the bead to areducing agent.

In some cases, chitosan, a linear polysaccharide polymer, may becrosslinked with glutaraldehyde via hydrophilic chains to form a bead.Crosslinking of chitosan polymers may be achieved by chemical reactionsthat are initiated by heat, pressure, change in pH, and/or radiation.

In some cases, a bead may comprise an acrydite moiety, which in certainaspects may be used to attach one or more nucleic acid molecules (e.g.,barcode sequence, barcoded nucleic acid molecule, barcodedoligonucleotide, primer, or other oligonucleotide) to the bead. In somecases, an acrydite moiety can refer to an acrydite analogue generatedfrom the reaction of acrydite with one or more species, such as, thereaction of acrydite with other monomers and cross-linkers during apolymerization reaction. Acrydite moieties may be modified to formchemical bonds with a species to be attached, such as a nucleic acidmolecule (e.g., barcode sequence, barcoded nucleic acid molecule,barcoded oligonucleotide, primer, or other oligonucleotide). Acryditemoieties may be modified with thiol groups capable of forming adisulfide bond or may be modified with groups already comprising adisulfide bond. The thiol or disulfide (via disulfide exchange) may beused as an anchor point for a species to be attached or another part ofthe acrydite moiety may be used for attachment. In some cases,attachment can be reversible, such that when the disulfide bond isbroken (e.g., in the presence of a reducing agent), the attached speciesis released from the bead. In other cases, an acrydite moiety cancomprise a reactive hydroxyl group that may be used for attachment.

Functionalization of beads for attachment of nucleic acid molecules(e.g., oligonucleotides) may be achieved through a wide range ofdifferent approaches, including activation of chemical groups within apolymer, incorporation of active or activatable functional groups in thepolymer structure, or attachment at the pre-polymer or monomer stage inbead production.

For example, precursors (e.g., monomers, cross-linkers) that arepolymerized to form a bead may comprise acrydite moieties, such thatwhen a bead is generated, the bead also comprises acrydite moieties. Theacrydite moieties can be attached to a nucleic acid molecule (e.g.,oligonucleotide), which may include a priming sequence (e.g., a primerfor amplifying target nucleic acids, random primer, primer sequence formessenger RNA) and/or one or more barcode sequences. The one morebarcode sequences may include sequences that are the same for allnucleic acid molecules coupled to a given bead and/or sequences that aredifferent across all nucleic acid molecules coupled to the given bead.The nucleic acid molecule may be incorporated into the bead.

In some cases, the nucleic acid molecule can comprise a functionalsequence, for example, for attachment to a sequencing flow cell, suchas, for example, a P5 sequence for Illumina® sequencing. In some cases,the nucleic acid molecule or derivative thereof (e.g., oligonucleotideor polynucleotide generated from the nucleic acid molecule) can compriseanother functional sequence, such as, for example, a P7 sequence forattachment to a sequencing flow cell for Illumina sequencing. In somecases, the nucleic acid molecule can comprise a barcode sequence. Insome cases, the primer can further comprise a unique molecularidentifier (UMI). In some cases, the primer can comprise an R1 primersequence for Illumina sequencing. In some cases, the primer can comprisean R2 primer sequence for Illumina sequencing. Examples of such nucleicacid molecules (e.g., oligonucleotides, polynucleotides, etc.) and usesthereof, as may be used with compositions, devices, methods and systemsof the present disclosure, are provided in U.S. Patent Pub. Nos.2014/0378345 and 2015/0376609, each of which is entirely incorporatedherein by reference.

FIG. 8 illustrates an example of a barcode carrying bead. A nucleic acidmolecule 802, such as an oligonucleotide, can be coupled to a bead 804by a releasable linkage 806, such as, for example, a disulfide linker.The same bead 804 may be coupled (e.g., via releasable linkage) to oneor more other nucleic acid molecules 818, 820. The nucleic acid molecule802 may be or comprise a barcode. As noted elsewhere herein, thestructure of the barcode may comprise a number of sequence elements. Thenucleic acid molecule 802 may comprise a functional sequence 808 thatmay be used in subsequent processing. For example, the functionalsequence 808 may include one or more of a sequencer specific flow cellattachment sequence (e.g., a P5 sequence for Illumina® sequencingsystems) and a sequencing primer sequence (e.g., a R1 primer forIllumina® sequencing systems). The nucleic acid molecule 802 maycomprise a barcode sequence 810 for use in barcoding the sample (e.g.,DNA, RNA, protein, etc.). In some cases, the barcode sequence 810 can bebead-specific such that the barcode sequence 810 is common to allnucleic acid molecules (e.g., including nucleic acid molecule 802)coupled to the same bead 804. Alternatively or in addition, the barcodesequence 810 can be partition-specific such that the barcode sequence810 is common to all nucleic acid molecules coupled to one or more beadsthat are partitioned into the same partition. The nucleic acid molecule802 may comprise a specific priming sequence 812, such as an mRNAspecific priming sequence (e.g., poly-T sequence), a targeted primingsequence, and/or a random priming sequence. The nucleic acid molecule802 may comprise an anchoring sequence 814 to ensure that the specificpriming sequence 812 hybridizes at the sequence end (e.g., of the mRNA).For example, the anchoring sequence 814 can include a random shortsequence of nucleotides, such as a 1-mer, 2-mer, 3-mer or longersequence, which can ensure that a poly-T segment is more likely tohybridize at the sequence end of the poly-A tail of the mRNA.

The nucleic acid molecule 802 may comprise a unique molecularidentifying sequence 816 (e.g., unique molecular identifier (UMI)). Insome cases, the unique molecular identifying sequence 816 may comprisefrom about 5 to about 8 nucleotides. Alternatively, the unique molecularidentifying sequence 816 may compress less than about 5 or more thanabout 8 nucleotides. The unique molecular identifying sequence 816 maybe a unique sequence that varies across individual nucleic acidmolecules (e.g., 802, 818, 820, etc.) coupled to a single bead (e.g.,bead 804). In some cases, the unique molecular identifying sequence 816may be a random sequence (e.g., such as a random N-mer sequence). Forexample, the UMI may provide a unique identifier of the starting mRNAmolecule that was captured, in order to allow quantitation of the numberof original expressed RNA. As will be appreciated, although FIG. 8 showsthree nucleic acid molecules 802, 818, 820 coupled to the surface of thebead 804, an individual bead may be coupled to any number of individualnucleic acid molecules, for example, from one to tens to hundreds ofthousands or even millions of individual nucleic acid molecules. Therespective barcodes for the individual nucleic acid molecules cancomprise both common sequence segments or relatively common sequencesegments (e.g., 808, 810, 812, etc.) and variable or unique sequencesegments (e.g., 816) between different individual nucleic acid moleculescoupled to the same bead.

In operation, a biological particle (e.g., cell, DNA, RNA, etc.) can beco-partitioned along with a barcode bearing bead 804. The barcodednucleic acid molecules 802, 818, 820 can be released from the bead 804in the partition. By way of example, in the context of analyzing sampleRNA, the poly-T segment (e.g., 812) of one of the released nucleic acidmolecules (e.g., 802) can hybridize to the poly-A tail of a mRNAmolecule. Reverse transcription may result in a cDNA transcript of themRNA, but which transcript includes each of the sequence segments 808,810, 816 of the nucleic acid molecule 802. Because the nucleic acidmolecule 802 comprises an anchoring sequence 814, it will more likelyhybridize to and prime reverse transcription at the sequence end of thepoly-A tail of the mRNA. Within any given partition, all of the cDNAtranscripts of the individual mRNA molecules may include a commonbarcode sequence segment 810. However, the transcripts made from thedifferent mRNA molecules within a given partition may vary at the uniquemolecular identifying sequence 812 segment (e.g., UMI segment).Beneficially, even following any subsequent amplification of thecontents of a given partition, the number of different UMIs can beindicative of the quantity of mRNA originating from a given partition,and thus from the biological particle (e.g., cell). As noted above, thetranscripts can be amplified, cleaned up and sequenced to identify thesequence of the cDNA transcript of the mRNA, as well as to sequence thebarcode segment and the UMI segment. While a poly-T primer sequence isdescribed, other targeted or random priming sequences may also be usedin priming the reverse transcription reaction. Likewise, althoughdescribed as releasing the barcoded oligonucleotides into the partition,in some cases, the nucleic acid molecules bound to the bead (e.g., gelbead) may be used to hybridize and capture the mRNA on the solid phaseof the bead, for example, in order to facilitate the separation of theRNA from other cell contents.

In some cases, precursors comprising a functional group that is reactiveor capable of being activated such that it becomes reactive can bepolymerized with other precursors to generate gel beads comprising theactivated or activatable functional group. The functional group may thenbe used to attach additional species (e.g., disulfide linkers, primers,other oligonucleotides, etc.) to the gel beads. For example, someprecursors comprising a carboxylic acid (COOH) group can co-polymerizewith other precursors to form a gel bead that also comprises a COOHfunctional group. In some cases, acrylic acid (a species comprising freeCOOH groups), acrylamide, and bis(acryloyl)cystamine can beco-polymerized together to generate a gel bead comprising free COOHgroups. The COOH groups of the gel bead can be activated (e.g., via1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) andN-Hydroxysuccinimide (NHS) or4-(4,6-Dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride(DMTMM)) such that they are reactive (e.g., reactive to amine functionalgroups where EDC/NHS or DMTMM are used for activation). The activatedCOOH groups can then react with an appropriate species (e.g., a speciescomprising an amine functional group where the carboxylic acid groupsare activated to be reactive with an amine functional group) comprisinga moiety to be linked to the bead.

Beads comprising disulfide linkages in their polymeric network may befunctionalized with additional species via reduction of some of thedisulfide linkages to free thiols. The disulfide linkages may be reducedvia, for example, the action of a reducing agent (e.g., DTT, TCEP, etc.)to generate free thiol groups, without dissolution of the bead. Freethiols of the beads can then react with free thiols of a species or aspecies comprising another disulfide bond (e.g., via thiol-disulfideexchange) such that the species can be linked to the beads (e.g., via agenerated disulfide bond). In some cases, free thiols of the beads mayreact with any other suitable group. For example, free thiols of thebeads may react with species comprising an acrydite moiety. The freethiol groups of the beads can react with the acrydite via Michaeladdition chemistry, such that the species comprising the acrydite islinked to the bead. In some cases, uncontrolled reactions can beprevented by inclusion of a thiol capping agent such asN-ethylmalieamide or iodoacetate.

Activation of disulfide linkages within a bead can be controlled suchthat only a small number of disulfide linkages are activated. Controlmay be exerted, for example, by controlling the concentration of areducing agent used to generate free thiol groups and/or concentrationof reagents used to form disulfide bonds in bead polymerization. In somecases, a low concentration (e.g., molecules of reducing agent:gel beadratios of less than or equal to about 1:100,000,000,000, less than orequal to about 1:10,000,000,000, less than or equal to about1:1,000,000,000, less than or equal to about 1:100,000,000, less than orequal to about 1:10,000,000, less than or equal to about 1:1,000,000,less than or equal to about 1:100,000, less than or equal to about1:10,000) of reducing agent may be used for reduction. Controlling thenumber of disulfide linkages that are reduced to free thiols may beuseful in ensuring bead structural integrity during functionalization.In some cases, optically-active agents, such as fluorescent dyes may becoupled to beads via free thiol groups of the beads and used to quantifythe number of free thiols present in a bead and/or track a bead.

In some cases, addition of moieties to a gel bead after gel beadformation may be advantageous. For example, addition of anoligonucleotide (e.g., barcoded oligonucleotide) after gel beadformation may avoid loss of the species during chain transfertermination that can occur during polymerization. Moreover, smallerprecursors (e.g., monomers or cross linkers that do not comprise sidechain groups and linked moieties) may be used for polymerization and canbe minimally hindered from growing chain ends due to viscous effects. Insome cases, functionalization after gel bead synthesis can minimizeexposure of species (e.g., oligonucleotides) to be loaded withpotentially damaging agents (e.g., free radicals) and/or chemicalenvironments. In some cases, the generated gel may possess an uppercritical solution temperature (UCST) that can permit temperature drivenswelling and collapse of a bead. Such functionality may aid inoligonucleotide (e.g., a primer) infiltration into the bead duringsubsequent functionalization of the bead with the oligonucleotide.Post-production functionalization may also be useful in controllingloading ratios of species in beads, such that, for example, thevariability in loading ratio is minimized. Species loading may also beperformed in a batch process such that a plurality of beads can befunctionalized with the species in a single batch.

A bead injected or otherwise introduced into a partition may comprisereleasably, cleavably, or reversibly attached barcodes. A bead injectedor otherwise introduced into a partition may comprise activatablebarcodes. A bead injected or otherwise introduced into a partition maybe degradable, disruptable, or dissolvable beads.

Barcodes can be releasably, cleavably or reversibly attached to thebeads such that barcodes can be released or be releasable throughcleavage of a linkage between the barcode molecule and the bead, orreleased through degradation of the underlying bead itself, allowing thebarcodes to be accessed or be accessible by other reagents, or both. Innon-limiting examples, cleavage may be achieved through reduction ofdi-sulfide bonds, use of restriction enzymes, photo-activated cleavage,or cleavage via other types of stimuli (e.g., chemical, thermal, pH,enzymatic, etc.) and/or reactions, such as described elsewhere herein.Releasable barcodes may sometimes be referred to as being activatable,in that they are available for reaction once released. Thus, forexample, an activatable barcode may be activated by releasing thebarcode from a bead (or other suitable type of partition describedherein). Other activatable configurations are also envisioned in thecontext of the described methods and systems.

In addition to, or as an alternative to the cleavable linkages betweenthe beads and the associated molecules, such as barcode containingnucleic acid molecules (e.g., barcoded oligonucleotides), the beads maybe degradable, disruptable, or dissolvable spontaneously or uponexposure to one or more stimuli (e.g., temperature changes, pH changes,exposure to particular chemical species or phase, exposure to light,reducing agent, etc.). In some cases, a bead may be dissolvable, suchthat material components of the beads are solubilized when exposed to aparticular chemical species or an environmental change, such as a changetemperature or a change in pH. In some cases, a gel bead can be degradedor dissolved at elevated temperature and/or in basic conditions. In somecases, a bead may be thermally degradable such that when the bead isexposed to an appropriate change in temperature (e.g., heat), the beaddegrades. Degradation or dissolution of a bead bound to a species (e.g.,a nucleic acid molecule, e.g., barcoded oligonucleotide) may result inrelease of the species from the bead.

As will be appreciated from the above disclosure, the degradation of abead may refer to the disassociation of a bound or entrained speciesfrom a bead, both with and without structurally degrading the physicalbead itself. For example, the degradation of the bead may involvecleavage of a cleavable linkage via one or more species and/or methodsdescribed elsewhere herein. In another example, entrained species may bereleased from beads through osmotic pressure differences due to, forexample, changing chemical environments. By way of example, alterationof bead pore sizes due to osmotic pressure differences can generallyoccur without structural degradation of the bead itself. In some cases,an increase in pore size due to osmotic swelling of a bead can permitthe release of entrained species within the bead. In other cases,osmotic shrinking of a bead may cause a bead to better retain anentrained species due to pore size contraction.

A degradable bead may be introduced into a partition, such as a dropletof an emulsion or a well, such that the bead degrades within thepartition and any associated species (e.g., oligonucleotides) arereleased within the droplet when the appropriate stimulus is applied.The free species (e.g., oligonucleotides, nucleic acid molecules) mayinteract with other reagents contained in the partition. For example, apolyacrylamide bead comprising cystamine and linked, via a disulfidebond, to a barcode sequence, may be combined with a reducing agentwithin a droplet of a water-in-oil emulsion. Within the droplet, thereducing agent can break the various disulfide bonds, resulting in beaddegradation and release of the barcode sequence into the aqueous, innerenvironment of the droplet. In another example, heating of a dropletcomprising a bead-bound barcode sequence in basic solution may alsoresult in bead degradation and release of the attached barcode sequenceinto the aqueous, inner environment of the droplet.

Any suitable number of molecular tag molecules (e.g., primer, barcodedoligonucleotide) can be associated with a bead such that, upon releasefrom the bead, the molecular tag molecules (e.g., primer, e.g., barcodedoligonucleotide) are present in the partition at a pre-definedconcentration. Such pre-defined concentration may be selected tofacilitate certain reactions for generating a sequencing library, e.g.,amplification, within the partition. In some cases, the pre-definedconcentration of the primer can be limited by the process of producingnucleic acid molecule (e.g., oligonucleotide) bearing beads.

In some cases, beads can be non-covalently loaded with one or morereagents. The beads can be non-covalently loaded by, for instance,subjecting the beads to conditions sufficient to swell the beads,allowing sufficient time for the reagents to diffuse into the interiorsof the beads, and subjecting the beads to conditions sufficient tode-swell the beads. The swelling of the beads may be accomplished, forinstance, by placing the beads in a thermodynamically favorable solvent,subjecting the beads to a higher or lower temperature, subjecting thebeads to a higher or lower ion concentration, and/or subjecting thebeads to an electric field. The swelling of the beads may beaccomplished by various swelling methods. The de-swelling of the beadsmay be accomplished, for instance, by transferring the beads in athermodynamically unfavorable solvent, subjecting the beads to lower orhigh temperatures, subjecting the beads to a lower or higher ionconcentration, and/or removing an electric field. The de-swelling of thebeads may be accomplished by various de-swelling methods. Transferringthe beads may cause pores in the bead to shrink. The shrinking may thenhinder reagents within the beads from diffusing out of the interiors ofthe beads. The hindrance may be due to steric interactions between thereagents and the interiors of the beads. The transfer may beaccomplished microfluidically. For instance, the transfer may beachieved by moving the beads from one co-flowing solvent stream to adifferent co-flowing solvent stream. The swellability and/or pore sizeof the beads may be adjusted by changing the polymer composition of thebead.

In some cases, an acrydite moiety linked to a precursor, another specieslinked to a precursor, or a precursor itself can comprise a labile bond,such as chemically, thermally, or photo-sensitive bond e.g., disulfidebond, UV sensitive bond, or the like. Once acrydite moieties or othermoieties comprising a labile bond are incorporated into a bead, the beadmay also comprise the labile bond. The labile bond may be, for example,useful in reversibly linking (e.g., covalently linking) species (e.g.,barcodes, primers, etc.) to a bead. In some cases, a thermally labilebond may include a nucleic acid hybridization based attachment, e.g.,where an oligonucleotide is hybridized to a complementary sequence thatis attached to the bead, such that thermal melting of the hybridreleases the oligonucleotide, e.g., a barcode containing sequence, fromthe bead or microcapsule.

The addition of multiple types of labile bonds to a gel bead may resultin the generation of a bead capable of responding to varied stimuli.Each type of labile bond may be sensitive to an associated stimulus(e.g., chemical stimulus, light, temperature, enzymatic, etc.) such thatrelease of species attached to a bead via each labile bond may becontrolled by the application of the appropriate stimulus. Suchfunctionality may be useful in controlled release of species from a gelbead. In some cases, another species comprising a labile bond may belinked to a gel bead after gel bead formation via, for example, anactivated functional group of the gel bead as described above. As willbe appreciated, barcodes that are releasably, cleavably or reversiblyattached to the beads described herein include barcodes that arereleased or releasable through cleavage of a linkage between the barcodemolecule and the bead, or that are released through degradation of theunderlying bead itself, allowing the barcodes to be accessed oraccessible by other reagents, or both.

The barcodes that are releasable as described herein may sometimes bereferred to as being activatable, in that they are available forreaction once released. Thus, for example, an activatable barcode may beactivated by releasing the barcode from a bead (or other suitable typeof partition described herein). Other activatable configurations arealso envisioned in the context of the described methods and systems.

In addition to thermally cleavable bonds, disulfide bonds and UVsensitive bonds, other non-limiting examples of labile bonds that may becoupled to a precursor or bead include an ester linkage (e.g., cleavablewith an acid, a base, or hydroxylamine), a vicinal diol linkage (e.g.,cleavable via sodium periodate), a Diels-Alder linkage (e.g., cleavablevia heat), a sulfone linkage (e.g., cleavable via a base), a silyl etherlinkage (e.g., cleavable via an acid), a glycosidic linkage (e.g.,cleavable via an amylase), a peptide linkage (e.g., cleavable via aprotease), or a phosphodiester linkage (e.g., cleavable via a nuclease(e.g., DNAase)). A bond may be cleavable via other nucleic acid moleculetargeting enzymes, such as restriction enzymes (e.g., restrictionendonucleases), as described further below.

Species may be encapsulated in beads during bead generation (e.g.,during polymerization of precursors). Such species may or may notparticipate in polymerization. Such species may be entered intopolymerization reaction mixtures such that generated beads comprise thespecies upon bead formation. In some cases, such species may be added tothe gel beads after formation. Such species may include, for example,nucleic acid molecules (e.g., oligonucleotides), reagents for a nucleicacid amplification reaction (e.g., primers, polymerases, dNTPs,co-factors (e.g., ionic co-factors), buffers) including those describedherein, reagents for enzymatic reactions (e.g., enzymes, co-factors,substrates, buffers), reagents for nucleic acid modification reactionssuch as polymerization, ligation, or digestion, and/or reagents fortemplate preparation (e.g., tagmentation) for one or more sequencingplatforms (e.g., Nextera® for Illumina®). Such species may include oneor more enzymes described herein, including without limitation,polymerase, reverse transcriptase, restriction enzymes (e.g.,endonuclease), transposase, ligase, proteinase K, DNAse, etc. Suchspecies may include one or more reagents described elsewhere herein(e.g., lysis agents, inhibitors, inactivating agents, chelating agents,stimulus). Trapping of such species may be controlled by the polymernetwork density generated during polymerization of precursors, controlof ionic charge within the gel bead (e.g., via ionic species linked topolymerized species), or by the release of other species. Encapsulatedspecies may be released from a bead upon bead degradation and/or byapplication of a stimulus capable of releasing the species from thebead. Alternatively or in addition, species may be partitioned in apartition (e.g., droplet) during or subsequent to partition formation.Such species may include, without limitation, the abovementioned speciesthat may also be encapsulated in a bead.

A degradable bead may comprise one or more species with a labile bondsuch that, when the bead/species is exposed to the appropriate stimuli,the bond is broken and the bead degrades. The labile bond may be achemical bond (e.g., covalent bond, ionic bond) or may be another typeof physical interaction (e.g., van der Waals interactions, dipole-dipoleinteractions, etc.). In some cases, a crosslinker used to generate abead may comprise a labile bond. Upon exposure to the appropriateconditions, the labile bond can be broken and the bead degraded. Forexample, upon exposure of a polyacrylamide gel bead comprising cystaminecrosslinkers to a reducing agent, the disulfide bonds of the cystaminecan be broken and the bead degraded.

A degradable bead may be useful in more quickly releasing an attachedspecies (e.g., a nucleic acid molecule, a barcode sequence, a primer,etc) from the bead when the appropriate stimulus is applied to the beadas compared to a bead that does not degrade. For example, for a speciesbound to an inner surface of a porous bead or in the case of anencapsulated species, the species may have greater mobility andaccessibility to other species in solution upon degradation of the bead.In some cases, a species may also be attached to a degradable bead via adegradable linker (e.g., disulfide linker). The degradable linker mayrespond to the same stimuli as the degradable bead or the two degradablespecies may respond to different stimuli. For example, a barcodesequence may be attached, via a disulfide bond, to a polyacrylamide beadcomprising cystamine. Upon exposure of the barcoded-bead to a reducingagent, the bead degrades and the barcode sequence is released uponbreakage of both the disulfide linkage between the barcode sequence andthe bead and the disulfide linkages of the cystamine in the bead.

As will be appreciated from the above disclosure, while referred to asdegradation of a bead, in many instances as noted above, thatdegradation may refer to the disassociation of a bound or entrainedspecies from a bead, both with and without structurally degrading thephysical bead itself. For example, entrained species may be releasedfrom beads through osmotic pressure differences due to, for example,changing chemical environments. By way of example, alteration of beadpore sizes due to osmotic pressure differences can generally occurwithout structural degradation of the bead itself. In some cases, anincrease in pore size due to osmotic swelling of a bead can permit therelease of entrained species within the bead. In other cases, osmoticshrinking of a bead may cause a bead to better retain an entrainedspecies due to pore size contraction.

Where degradable beads are provided, it may be beneficial to avoidexposing such beads to the stimulus or stimuli that cause suchdegradation prior to a given time, in order to, for example, avoidpremature bead degradation and issues that arise from such degradation,including for example poor flow characteristics and aggregation. By wayof example, where beads comprise reducible cross-linking groups, such asdisulfide groups, it will be desirable to avoid contacting such beadswith reducing agents, e.g., DTT or other disulfide cleaving reagents. Insuch cases, treatment to the beads described herein will, in some casesbe provided free of reducing agents, such as DTT. Because reducingagents are often provided in commercial enzyme preparations, it may bedesirable to provide reducing agent free (or DTT free) enzymepreparations in treating the beads described herein. Examples of suchenzymes include, e.g., polymerase enzyme preparations, reversetranscriptase enzyme preparations, ligase enzyme preparations, as wellas many other enzyme preparations that may be used to treat the beadsdescribed herein. The terms “reducing agent free” or “DTT free”preparations can refer to a preparation having less than about 1/10,less than about 1/50, or even less than about 1/100 of the lower rangesfor such materials used in degrading the beads. For example, for DTT,the reducing agent free preparation can have less than about 0.01millimolar (mM), 0.005 mM, 0.001 mM DTT, 0.0005 mM DTT, or even lessthan about 0.0001 mM DTT. In many cases, the amount of DTT can beundetectable.

Numerous chemical triggers may be used to trigger the degradation ofbeads. Examples of these chemical changes may include, but are notlimited to pH-mediated changes to the integrity of a component withinthe bead, degradation of a component of a bead via cleavage ofcross-linked bonds, and depolymerization of a component of a bead.

In some embodiments, a bead may be formed from materials that comprisedegradable chemical crosslinkers, such as BAC or cystamine. Degradationof such degradable crosslinkers may be accomplished through a number ofmechanisms. In some examples, a bead may be contacted with a chemicaldegrading agent that may induce oxidation, reduction or other chemicalchanges. For example, a chemical degrading agent may be a reducingagent, such as dithiothreitol (DTT). Additional examples of reducingagents may include (3-mercaptoethanol, (2S)-2-amino-1,4-dimercaptobutane(dithiobutylamine or DTBA), tris(2-carboxyethyl) phosphine (TCEP), orcombinations thereof. A reducing agent may degrade the disulfide bondsformed between gel precursors forming the bead, and thus, degrade thebead. In other cases, a change in pH of a solution, such as an increasein pH, may trigger degradation of a bead. In other cases, exposure to anaqueous solution, such as water, may trigger hydrolytic degradation, andthus degradation of the bead. In some cases, any combination of stimulimay trigger degradation of a bead. For example, a change in pH mayenable a chemical agent (e.g., DTT) to become an effective reducingagent.

Beads may also be induced to release their contents upon the applicationof a thermal stimulus. A change in temperature can cause a variety ofchanges to a bead. For example, heat can cause a solid bead to liquefy.A change in heat may cause melting of a bead such that a portion of thebead degrades. In other cases, heat may increase the internal pressureof the bead components such that the bead ruptures or explodes. Heat mayalso act upon heat-sensitive polymers used as materials to constructbeads.

Any suitable agent may degrade beads. In some embodiments, changes intemperature or pH may be used to degrade thermo-sensitive orpH-sensitive bonds within beads. In some embodiments, chemical degradingagents may be used to degrade chemical bonds within beads by oxidation,reduction or other chemical changes. For example, a chemical degradingagent may be a reducing agent, such as DTT, wherein DTT may degrade thedisulfide bonds formed between a crosslinker and gel precursors, thusdegrading the bead. In some embodiments, a reducing agent may be addedto degrade the bead, which may or may not cause the bead to release itscontents. Examples of reducing agents may include dithiothreitol (DTT),β-mercaptoethanol, (2S)-2-amino-1,4-dimercaptobutane (dithiobutylamineor DTBA), tris(2-carboxyethyl) phosphine (TCEP), or combinationsthereof. The reducing agent may be present at a concentration of about0.1 mM, 0.5 mM, 1 mM, 5 mM, 10 mM. The reducing agent may be present ata concentration of at least about 0.1 mM, 0.5 mM, 1 mM, 5 mM, 10 mM, orgreater than 10 mM. The reducing agent may be present at concentrationof at most about 10 mM, 5 mM, 1 mM, 0.5 mM, 0.1 mM, or less.

Any suitable number of molecular tag molecules (e.g., primer, barcodedoligonucleotide) can be associated with a bead such that, upon releasefrom the bead, the molecular tag molecules (e.g., primer, e.g., barcodedoligonucleotide) are present in the partition at a pre-definedconcentration. Such pre-defined concentration may be selected tofacilitate certain reactions for generating a sequencing library, e.g.,amplification, within the partition. In some cases, the pre-definedconcentration of the primer can be limited by the process of producingoligonucleotide bearing beads.

Although FIG. 1 and FIG. 2 have been described in terms of providingsubstantially singly occupied partitions, above, in certain cases, itmay be desirable to provide multiply occupied partitions, e.g.,containing two, three, four or more cells and/or microcapsules (e.g.,beads) comprising barcoded nucleic acid molecules (e.g.,oligonucleotides) within a single partition. Accordingly, as notedabove, the flow characteristics of the biological particle and/or beadcontaining fluids and partitioning fluids may be controlled to providefor such multiply occupied partitions. In particular, the flowparameters may be controlled to provide a given occupancy rate atgreater than about 50% of the partitions, greater than about 75%, and insome cases greater than about 80%, 90%, 95%, or higher.

In some cases, additional microcapsules can be used to deliveradditional reagents to a partition. In such cases, it may beadvantageous to introduce different beads into a common channel ordroplet generation junction, from different bead sources (e.g.,containing different associated reagents) through different channelinlets into such common channel or droplet generation junction (e.g.,junction 210). In such cases, the flow and frequency of the differentbeads into the channel or junction may be controlled to provide for acertain ratio of microcapsules from each source, while ensuring a givenpairing or combination of such beads into a partition with a givennumber of biological particles (e.g., one biological particle and onebead per partition).

The partitions described herein may comprise small volumes, for example,less than about 10 microliters (μL), 5 μL, 1 μL, 900 picoliters (pL),800 pL, 700 pL, 600 pL, 500 pL, 400 pL, 300 pL, 200 pL, 100 pL, 50 pL,20 pL, 10 pL, 1 pL, 500 nanoliters (nL), 100 nL, 50 nL, or less.

For example, in the case of droplet based partitions, the droplets mayhave overall volumes that are less than about 1000 pL, 900 pL, 800 pL,700 pL, 600 pL, 500 pL, 400 pL, 300 pL, 200 pL, 100 pL, 50 pL, 20 pL, 10pL, 1 pL, or less. Where co-partitioned with microcapsules, it will beappreciated that the sample fluid volume, e.g., including co-partitionedbiological particles and/or beads, within the partitions may be lessthan about 90% of the above described volumes, less than about 80%, lessthan about 70%, less than about 60%, less than about 50%, less thanabout 40%, less than about 30%, less than about 20%, or less than about10% of the above described volumes.

As is described elsewhere herein, partitioning species may generate apopulation or plurality of partitions. In such cases, any suitablenumber of partitions can be generated or otherwise provided. Forexample, at least about 1,000 partitions, at least about 5,000partitions, at least about 10,000 partitions, at least about 50,000partitions, at least about 100,000 partitions, at least about 500,000partitions, at least about 1,000,000 partitions, at least about5,000,000 partitions at least about 10,000,000 partitions, at leastabout 50,000,000 partitions, at least about 100,000,000 partitions, atleast about 500,000,000 partitions, at least about 1,000,000,000partitions, or more partitions can be generated or otherwise provided.Moreover, the plurality of partitions may comprise both unoccupiedpartitions (e.g., empty partitions) and occupied partitions.

Reagents

In accordance with certain aspects, biological particles may bepartitioned along with lysis reagents in order to release the contentsof the biological particles within the partition. In such cases, thelysis agents can be contacted with the biological particle suspensionconcurrently with, or immediately prior to, the introduction of thebiological particles into the partitioning junction/droplet generationzone (e.g., junction 210), such as through an additional channel orchannels upstream of the channel junction. In accordance with otheraspects, additionally or alternatively, biological particles may bepartitioned along with other reagents, as will be described furtherbelow.

FIG. 3 shows an example of a microfluidic channel structure 300 forco-partitioning biological particles and reagents. The channel structure300 can include channel segments 301, 302, 304, 306 and 308. Channelsegments 301 and 302 communicate at a first channel junction 309.Channel segments 302, 304, 306, and 308 communicate at a second channeljunction 310.

In an example operation, the channel segment 301 may transport anaqueous fluid 312 that includes a plurality of biological particles 314along the channel segment 301 into the second junction 310. As analternative or in addition to, channel segment 301 may transport beads(e.g., gel beads). The beads may comprise barcode molecules.

For example, the channel segment 301 may be connected to a reservoircomprising an aqueous suspension of biological particles 314. Upstreamof, and immediately prior to reaching, the second junction 310, thechannel segment 301 may meet the channel segment 302 at the firstjunction 309. The channel segment 302 may transport a plurality ofreagents 315 (e.g., lysis agents) suspended in the aqueous fluid 312along the channel segment 302 into the first junction 309. For example,the channel segment 302 may be connected to a reservoir comprising thereagents 315. After the first junction 309, the aqueous fluid 312 in thechannel segment 301 can carry both the biological particles 314 and thereagents 315 towards the second junction 310. In some instances, theaqueous fluid 312 in the channel segment 301 can include one or morereagents, which can be the same or different reagents as the reagents315. A second fluid 316 that is immiscible with the aqueous fluid 312(e.g., oil) can be delivered to the second junction 310 from each ofchannel segments 304 and 306. Upon meeting of the aqueous fluid 312 fromthe channel segment 301 and the second fluid 316 from each of channelsegments 304 and 306 at the second channel junction 310, the aqueousfluid 312 can be partitioned as discrete droplets 318 in the secondfluid 316 and flow away from the second junction 310 along channelsegment 308. The channel segment 308 may deliver the discrete droplets318 to an outlet reservoir fluidly coupled to the channel segment 308,where they may be harvested.

The second fluid 316 can comprise an oil, such as a fluorinated oil,that includes a fluorosurfactant for stabilizing the resulting droplets,for example, inhibiting subsequent coalescence of the resulting droplets318.

A discrete droplet generated may include an individual biologicalparticle 314 and/or one or more reagents 315. In some instances, adiscrete droplet generated may include a barcode carrying bead (notshown), such as via other microfluidics structures described elsewhereherein. In some instances, a discrete droplet may be unoccupied (e.g.,no reagents, no biological particles).

Beneficially, when lysis reagents and biological particles areco-partitioned, the lysis reagents can facilitate the release of thecontents of the biological particles within the partition. The contentsreleased in a partition may remain discrete from the contents of otherpartitions.

As will be appreciated, the channel segments described herein may becoupled to any of a variety of different fluid sources or receivingcomponents, including reservoirs, tubing, manifolds, or fluidiccomponents of other systems. As will be appreciated, the microfluidicchannel structure 300 may have other geometries. For example, amicrofluidic channel structure can have more than two channel junctions.For example, a microfluidic channel structure can have 2, 3, 4, 5channel segments or more each carrying the same or different types ofbeads, reagents, and/or biological particles that meet at a channeljunction. Fluid flow in each channel segment may be controlled tocontrol the partitioning of the different elements into droplets. Fluidmay be directed flow along one or more channels or reservoirs via one ormore fluid flow units. A fluid flow unit can comprise compressors (e.g.,providing positive pressure), pumps (e.g., providing negative pressure),actuators, and the like to control flow of the fluid. Fluid may also orotherwise be controlled via applied pressure differentials, centrifugalforce, electrokinetic pumping, vacuum, capillary or gravity flow, or thelike.

Examples of lysis agents include bioactive reagents, such as lysisenzymes that are used for lysis of different cell types, e.g., grampositive or negative bacteria, plants, yeast, mammalian, etc., such aslysozymes, achromopeptidase, lysostaphin, labiase, kitalase, lyticase,and a variety of other lysis enzymes available from, e.g.,Sigma-Aldrich, Inc. (St Louis, Mo.), as well as other commerciallyavailable lysis enzymes. Other lysis agents may additionally oralternatively be co-partitioned with the biological particles to causethe release of the biological particles's contents into the partitions.For example, in some cases, surfactant-based lysis solutions may be usedto lyse cells, although these may be less desirable for emulsion basedsystems where the surfactants can interfere with stable emulsions. Insome cases, lysis solutions may include non-ionic surfactants such as,for example, TritonX-100 and Tween 20. In some cases, lysis solutionsmay include ionic surfactants such as, for example, sarcosyl and sodiumdodecyl sulfate (SDS). Electroporation, thermal, acoustic or mechanicalcellular disruption may also be used in certain cases, e.g.,non-emulsion based partitioning such as encapsulation of biologicalparticles that may be in addition to or in place of dropletpartitioning, where any pore size of the encapsulate is sufficientlysmall to retain nucleic acid fragments of a given size, followingcellular disruption.

Alternatively or in addition to the lysis agents co-partitioned with thebiological particles described above, other reagents can also beco-partitioned with the biological particles, including, for example,DNase and RNase inactivating agents or inhibitors, such as proteinase K,chelating agents, such as EDTA, and other reagents employed in removingor otherwise reducing negative activity or impact of different celllysate components on subsequent processing of nucleic acids. Inaddition, in the case of encapsulated biological particles, thebiological particles may be exposed to an appropriate stimulus torelease the biological particles or their contents from a co-partitionedmicrocapsule. For example, in some cases, a chemical stimulus may beco-partitioned along with an encapsulated biological particle to allowfor the degradation of the microcapsule and release of the cell or itscontents into the larger partition. In some cases, this stimulus may bethe same as the stimulus described elsewhere herein for release ofnucleic acid molecules (e.g., oligonucleotides) from their respectivemicrocapsule (e.g., bead). In alternative aspects, this may be adifferent and non-overlapping stimulus, in order to allow anencapsulated biological particle to be released into a partition at adifferent time from the release of nucleic acid molecules into the samepartition.

Additional reagents may also be co-partitioned with the biologicalparticles, such as endonucleases to fragment a biological particle'sDNA, DNA polymerase enzymes and dNTPs used to amplify the biologicalparticle's nucleic acid fragments and to attach the barcode moleculartags to the amplified fragments. Other enzymes may be co-partitioned,including without limitation, polymerase, transposase, ligase,proteinase K, DNAse, etc. Additional reagents may also include reversetranscriptase enzymes, including enzymes with terminal transferaseactivity, primers and oligonucleotides, and switch oligonucleotides(also referred to herein as “switch oligos” or “template switchingoligonucleotides”) which can be used for template switching. In somecases, template switching can be used to increase the length of a cDNA.In some cases, template switching can be used to append a predefinednucleic acid sequence to the cDNA. In an example of template switching,cDNA can be generated from reverse transcription of a template, e.g.,cellular mRNA, where a reverse transcriptase with terminal transferaseactivity can add additional nucleotides, e.g., polyC, to the cDNA in atemplate independent manner. Switch oligos can include sequencescomplementary to the additional nucleotides, e.g., polyG. The additionalnucleotides (e.g., polyC) on the cDNA can hybridize to the additionalnucleotides (e.g., polyG) on the switch oligo, whereby the switch oligocan be used by the reverse transcriptase as template to further extendthe cDNA. Template switching oligonucleotides may comprise ahybridization region and a template region. The hybridization region cancomprise any sequence capable of hybridizing to the target. In somecases, as previously described, the hybridization region comprises aseries of G bases to complement the overhanging C bases at the 3′ end ofa cDNA molecule. The series of G bases may comprise 1 G base, 2 G bases,3 G bases, 4 G bases, 5 G bases or more than 5 G bases. The templatesequence can comprise any sequence to be incorporated into the cDNA. Insome cases, the template region comprises at least 1 (e.g., at least 2,3, 4, 5 or more) tag sequences and/or functional sequences. Switcholigos may comprise deoxyribonucleic acids; ribonucleic acids; modifiednucleic acids including 2-Aminopurine, 2,6-Diaminopurine (2-Amino-dA),inverted dT, 5-Methyl dC, 2′-deoxyInosine, Super T(5-hydroxybutynl-2′-deoxyuridine), Super G (8-aza-7-deazaguanosine),locked nucleic acids (LNAs), unlocked nucleic acids (UNAs, e.g., UNA-A,UNA-U, UNA-C, UNA-G), Iso-dG, Iso-dC, 2′ Fluoro bases (e.g., Fluoro C,Fluoro U, Fluoro A, and Fluoro G), or any combination.

In some cases, the length of a switch oligo may be at least about 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58,59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76,77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94,95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109,110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123,124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137,138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151,152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165,166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179,180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193,194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207,208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221,222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235,236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249 or250 nucleotides or longer.

In some cases, the length of a switch oligo may be at most about 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58,59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76,77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94,95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109,110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123,124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137,138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151,152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165,166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179,180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193,194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207,208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221,222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235,236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249 or250 nucleotides.

Once the contents of the cells are released into their respectivepartitions, the macromolecular components (e.g., macromolecularconstituents of biological particles, such as RNA, DNA, or proteins)contained therein may be further processed within the partitions. Inaccordance with the methods and systems described herein, themacromolecular component contents of individual biological particles canbe provided with unique identifiers such that, upon characterization ofthose macromolecular components they may be attributed as having beenderived from the same biological particle or particles. The ability toattribute characteristics to individual biological particles or groupsof biological particles is provided by the assignment of uniqueidentifiers specifically to an individual biological particle or groupsof biological particles. Unique identifiers, e.g., in the form ofnucleic acid barcodes can be assigned or associated with individualbiological particles or populations of biological particles, in order totag or label the biological particle's macromolecular components (and asa result, its characteristics) with the unique identifiers. These uniqueidentifiers can then be used to attribute the biological particle'scomponents and characteristics to an individual biological particle orgroup of biological particles.

In some aspects, this is performed by co-partitioning the individualbiological particle or groups of biological particles with the uniqueidentifiers, such as described above (with reference to FIG. 2). In someaspects, the unique identifiers are provided in the form of nucleic acidmolecules (e.g., oligonucleotides) that comprise nucleic acid barcodesequences that may be attached to or otherwise associated with thenucleic acid contents of individual biological particle, or to othercomponents of the biological particle, and particularly to fragments ofthose nucleic acids. The nucleic acid molecules are partitioned suchthat as between nucleic acid molecules in a given partition, the nucleicacid barcode sequences contained therein are the same, but as betweendifferent partitions, the nucleic acid molecule can, and do havediffering barcode sequences, or at least represent a large number ofdifferent barcode sequences across all of the partitions in a givenanalysis. In some aspects, only one nucleic acid barcode sequence can beassociated with a given partition, although in some cases, two or moredifferent barcode sequences may be present.

The nucleic acid barcode sequences can include from about 6 to about 20or more nucleotides within the sequence of the nucleic acid molecules(e.g., oligonucleotides). The nucleic acid barcode sequences can includefrom about 6 to about 20, 30, 40, 50, 60, 70, 80, 90, 100 or morenucleotides. In some cases, the length of a barcode sequence may beabout 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 nucleotidesor longer. In some cases, the length of a barcode sequence may be atleast about 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20nucleotides or longer. In some cases, the length of a barcode sequencemay be at most about 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,20 nucleotides or shorter. These nucleotides may be completelycontiguous, i.e., in a single stretch of adjacent nucleotides, or theymay be separated into two or more separate subsequences that areseparated by 1 or more nucleotides. In some cases, separated barcodesubsequences can be from about 4 to about 16 nucleotides in length. Insome cases, the barcode subsequence may be about 4, 5, 6, 7, 8, 9, 10,11, 12, 13, 14, 15, 16 nucleotides or longer. In some cases, the barcodesubsequence may be at least about 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16 nucleotides or longer. In some cases, the barcode subsequence maybe at most about 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16nucleotides or shorter.

The co-partitioned nucleic acid molecules can also comprise otherfunctional sequences useful in the processing of the nucleic acids fromthe co-partitioned biological particles. These sequences include, e.g.,targeted or random/universal amplification primer sequences foramplifying the genomic DNA from the individual biological particleswithin the partitions while attaching the associated barcode sequences,sequencing primers or primer recognition sites, hybridization or probingsequences, e.g., for identification of presence of the sequences or forpulling down barcoded nucleic acids, or any of a number of otherpotential functional sequences. Other mechanisms of co-partitioningoligonucleotides may also be employed, including, e.g., coalescence oftwo or more droplets, where one droplet contains oligonucleotides, ormicrodispensing of oligonucleotides into partitions, e.g., dropletswithin microfluidic systems.

In an example, microcapsules, such as beads, are provided that eachinclude large numbers of the above described barcoded nucleic acidmolecules (e.g., barcoded oligonucleotides) releasably attached to thebeads, where all of the nucleic acid molecules attached to a particularbead will include the same nucleic acid barcode sequence, but where alarge number of diverse barcode sequences are represented across thepopulation of beads used. In some embodiments, hydrogel beads, e.g.,comprising polyacrylamide polymer matrices, are used as a solid supportand delivery vehicle for the nucleic acid molecules into the partitions,as they are capable of carrying large numbers of nucleic acid molecules,and may be configured to release those nucleic acid molecules uponexposure to a particular stimulus, as described elsewhere herein. Insome cases, the population of beads provides a diverse barcode sequencelibrary that includes at least about 1,000 different barcode sequences,at least about 5,000 different barcode sequences, at least about 10,000different barcode sequences, at least about 50,000 different barcodesequences, at least about 100,000 different barcode sequences, at leastabout 1,000,000 different barcode sequences, at least about 5,000,000different barcode sequences, or at least about 10,000,000 differentbarcode sequences, or more. Additionally, each bead can be provided withlarge numbers of nucleic acid (e.g., oligonucleotide) moleculesattached. In particular, the number of molecules of nucleic acidmolecules including the barcode sequence on an individual bead can be atleast about 1,000 nucleic acid molecules, at least about 5,000 nucleicacid molecules, at least about 10,000 nucleic acid molecules, at leastabout 50,000 nucleic acid molecules, at least about 100,000 nucleic acidmolecules, at least about 500,000 nucleic acids, at least about1,000,000 nucleic acid molecules, at least about 5,000,000 nucleic acidmolecules, at least about 10,000,000 nucleic acid molecules, at leastabout 50,000,000 nucleic acid molecules, at least about 100,000,000nucleic acid molecules, at least about 250,000,000 nucleic acidmolecules and in some cases at least about 1 billion nucleic acidmolecules, or more. Nucleic acid molecules of a given bead can includeidentical (or common) barcode sequences, different barcode sequences, ora combination of both. Nucleic acid molecules of a given bead caninclude multiple sets of nucleic acid molecules. Nucleic acid moleculesof a given set can include identical barcode sequences. The identicalbarcode sequences can be different from barcode sequences of nucleicacid molecules of another set.

Moreover, when the population of beads is partitioned, the resultingpopulation of partitions can also include a diverse barcode library thatincludes at least about 1,000 different barcode sequences, at leastabout 5,000 different barcode sequences, at least about 10,000 differentbarcode sequences, at least at least about 50,000 different barcodesequences, at least about 100,000 different barcode sequences, at leastabout 1,000,000 different barcode sequences, at least about 5,000,000different barcode sequences, or at least about 10,000,000 differentbarcode sequences. Additionally, each partition of the population caninclude at least about 1,000 nucleic acid molecules, at least about5,000 nucleic acid molecules, at least about 10,000 nucleic acidmolecules, at least about 50,000 nucleic acid molecules, at least about100,000 nucleic acid molecules, at least about 500,000 nucleic acids, atleast about 1,000,000 nucleic acid molecules, at least about 5,000,000nucleic acid molecules, at least about 10,000,000 nucleic acidmolecules, at least about 50,000,000 nucleic acid molecules, at leastabout 100,000,000 nucleic acid molecules, at least about 250,000,000nucleic acid molecules and in some cases at least about 1 billionnucleic acid molecules.

In some cases, it may be desirable to incorporate multiple differentbarcodes within a given partition, either attached to a single ormultiple beads within the partition. For example, in some cases, amixed, but known set of barcode sequences may provide greater assuranceof identification in the subsequent processing, e.g., by providing astronger address or attribution of the barcodes to a given partition, asa duplicate or independent confirmation of the output from a givenpartition.

The nucleic acid molecules (e.g., oligonucleotides) are releasable fromthe beads upon the application of a particular stimulus to the beads. Insome cases, the stimulus may be a photo-stimulus, e.g., through cleavageof a photo-labile linkage that releases the nucleic acid molecules. Inother cases, a thermal stimulus may be used, where elevation of thetemperature of the beads environment will result in cleavage of alinkage or other release of the nucleic acid molecules form the beads.In still other cases, a chemical stimulus can be used that cleaves alinkage of the nucleic acid molecules to the beads, or otherwise resultsin release of the nucleic acid molecules from the beads. In one case,such compositions include the polyacrylamide matrices described abovefor encapsulation of biological particles, and may be degraded forrelease of the attached nucleic acid molecules through exposure to areducing agent, such as DTT.

In some aspects, provided are systems and methods for controlledpartitioning. Droplet size may be controlled by adjusting certaingeometric features in channel architecture (e.g., microfluidics channelarchitecture). For example, an expansion angle, width, and/or length ofa channel may be adjusted to control droplet size.

FIG. 4 shows an example of a microfluidic channel structure for thecontrolled partitioning of beads into discrete droplets. A channelstructure 400 can include a channel segment 402 communicating at achannel junction 406 (or intersection) with a reservoir 404. Thereservoir 404 can be a chamber. Any reference to “reservoir,” as usedherein, can also refer to a “chamber.” In operation, an aqueous fluid408 that includes suspended beads 412 may be transported along thechannel segment 402 into the junction 406 to meet a second fluid 410that is immiscible with the aqueous fluid 408 in the reservoir 404 tocreate droplets 416, 418 of the aqueous fluid 408 flowing into thereservoir 404. At the junction 406 where the aqueous fluid 408 and thesecond fluid 410 meet, droplets can form based on factors such as thehydrodynamic forces at the junction 406, flow rates of the two fluids408, 410, fluid properties, and certain geometric parameters (e.g., w,h₀, a, etc.) of the channel structure 400. A plurality of droplets canbe collected in the reservoir 404 by continuously injecting the aqueousfluid 408 from the channel segment 402 through the junction 406.

A discrete droplet generated may include a bead (e.g., as in occupieddroplets 416). Alternatively, a discrete droplet generated may includemore than one bead. Alternatively, a discrete droplet generated may notinclude any beads (e.g., as in unoccupied droplet 418). In someinstances, a discrete droplet generated may contain one or morebiological particles, as described elsewhere herein. In some instances,a discrete droplet generated may comprise one or more reagents, asdescribed elsewhere herein.

In some instances, the aqueous fluid 408 can have a substantiallyuniform concentration or frequency of beads 412. The beads 412 can beintroduced into the channel segment 402 from a separate channel (notshown in FIG. 4). The frequency of beads 412 in the channel segment 402may be controlled by controlling the frequency in which the beads 412are introduced into the channel segment 402 and/or the relative flowrates of the fluids in the channel segment 402 and the separate channel.In some instances, the beads can be introduced into the channel segment402 from a plurality of different channels, and the frequency controlledaccordingly.

In some instances, the aqueous fluid 408 in the channel segment 402 cancomprise biological particles (e.g., described with reference to FIGS. 1and 2). In some instances, the aqueous fluid 408 can have asubstantially uniform concentration or frequency of biologicalparticles. As with the beads, the biological particles can be introducedinto the channel segment 402 from a separate channel. The frequency orconcentration of the biological particles in the aqueous fluid 408 inthe channel segment 402 may be controlled by controlling the frequencyin which the biological particles are introduced into the channelsegment 402 and/or the relative flow rates of the fluids in the channelsegment 402 and the separate channel. In some instances, the biologicalparticles can be introduced into the channel segment 402 from aplurality of different channels, and the frequency controlledaccordingly. In some instances, a first separate channel can introducebeads and a second separate channel can introduce biological particlesinto the channel segment 402. The first separate channel introducing thebeads may be upstream or downstream of the second separate channelintroducing the biological particles.

The second fluid 410 can comprise an oil, such as a fluorinated oil,that includes a fluorosurfactant for stabilizing the resulting droplets,for example, inhibiting subsequent coalescence of the resultingdroplets.

In some instances, the second fluid 410 may not be subjected to and/ordirected to any flow in or out of the reservoir 404. For example, thesecond fluid 410 may be substantially stationary in the reservoir 404.In some instances, the second fluid 410 may be subjected to flow withinthe reservoir 404, but not in or out of the reservoir 404, such as viaapplication of pressure to the reservoir 404 and/or as affected by theincoming flow of the aqueous fluid 408 at the junction 406.Alternatively, the second fluid 410 may be subjected and/or directed toflow in or out of the reservoir 404. For example, the reservoir 404 canbe a channel directing the second fluid 410 from upstream to downstream,transporting the generated droplets.

The channel structure 400 at or near the junction 406 may have certaingeometric features that at least partly determine the sizes of thedroplets formed by the channel structure 400. The channel segment 402can have a height, h₀ and width, w, at or near the junction 406. By wayof example, the channel segment 402 can comprise a rectangularcross-section that leads to a reservoir 404 having a wider cross-section(such as in width or diameter). Alternatively, the cross-section of thechannel segment 402 can be other shapes, such as a circular shape,trapezoidal shape, polygonal shape, or any other shapes. The top andbottom walls of the reservoir 404 at or near the junction 406 can beinclined at an expansion angle, a. The expansion angle, a, allows thetongue (portion of the aqueous fluid 408 leaving channel segment 402 atjunction 406 and entering the reservoir 404 before droplet formation) toincrease in depth and facilitate decrease in curvature of theintermediately formed droplet. Droplet size may decrease with increasingexpansion angle. The resulting droplet radius, R_(d), may be predictedby the following equation for the aforementioned geometric parameters ofh₀, w, and α:

$R_{d} \approx {0.44\left( {1 + {2.2\sqrt{\tan \; \alpha}\frac{w}{h_{0}}}} \right)\frac{h_{0}}{\sqrt{\tan \; \alpha}}}$

By way of example, for a channel structure with w=21 μm, h=21 μm, andα=3°, the predicted droplet size is 121 μm. In another example, for achannel structure with w=25 h=25 μm, and α=5°, the predicted dropletsize is 123 μm. In another example, for a channel structure with w=28μm, h=28 μm, and α=7°, the predicted droplet size is 124 μm.

In some instances, the expansion angle, a, may be between a range offrom about 0.5° to about 4°, from about 0.1° to about 10°, or from about0° to about 90°. For example, the expansion angle can be at least about0.01°, 0.1°, 0.2°, 0.3°, 0.4°, 0.5°, 0.6°, 0.7°, 0.8°, 0.9°, 1°, 2°, 3°,4°, 5°, 6°, 7°, 8°, 9°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°,55°, 60°, 65°, 70°, 75°, 80°, 85°, or higher. In some instances, theexpansion angle can be at most about 89°, 88°, 87°, 86°, 85°, 84°, 83°,82°, 81°, 80°, 75°, 70°, 65°, 60°, 55°, 50°, 45°, 40°, 35°, 30°, 25°,20°, 15°, 10°, 9°, 8°, 7°, 6°, 5°, 4°, 3°, 2°, 1°, 0.1°, 0.01°, or less.In some instances, the width, w, can be between a range of from about100 micrometers (μm) to about 500 μm. In some instances, the width, w,can be between a range of from about 10 μm to about 200 μm.Alternatively, the width can be less than about 10 μm. Alternatively,the width can be greater than about 500 μm. In some instances, the flowrate of the aqueous fluid 408 entering the junction 406 can be betweenabout 0.04 microliters (μL)/minute (min) and about 40 μL/min. In someinstances, the flow rate of the aqueous fluid 408 entering the junction406 can be between about 0.01 microliters (μL)/minute (min) and about100 μL/min. Alternatively, the flow rate of the aqueous fluid 408entering the junction 406 can be less than about 0.01 μL/min.Alternatively, the flow rate of the aqueous fluid 408 entering thejunction 406 can be greater than about 40 μL/min, such as 45 μL/min, 50μL/min, 55 μL/min, 60 μL/min, 65 μL/min, 70 μL/min, 75 μL/min, 80μL/min, 85 μL/min, 90 μL/min, 95 μL/min, 100 μL/min, 110 μL/min, 120μL/min, 130 μL/min, 140 μL/min, 150 μL/min, or greater. At lower flowrates, such as flow rates of about less than or equal to 10microliters/minute, the droplet radius may not be dependent on the flowrate of the aqueous fluid 408 entering the junction 406.

In some instances, at least about 50% of the droplets generated can haveuniform size. In some instances, at least about 55%, 60%, 65%, 70%, 75%,80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or greater of the dropletsgenerated can have uniform size. Alternatively, less than about 50% ofthe droplets generated can have uniform size.

The throughput of droplet generation can be increased by increasing thepoints of generation, such as increasing the number of junctions (e.g.,junction 406) between aqueous fluid 408 channel segments (e.g., channelsegment 402) and the reservoir 404. Alternatively or in addition, thethroughput of droplet generation can be increased by increasing the flowrate of the aqueous fluid 408 in the channel segment 402.

FIG. 5 shows an example of a microfluidic channel structure forincreased droplet generation throughput. A microfluidic channelstructure 500 can comprise a plurality of channel segments 502 and areservoir 504. Each of the plurality of channel segments 502 may be influid communication with the reservoir 504. The channel structure 500can comprise a plurality of channel junctions 506 between the pluralityof channel segments 502 and the reservoir 504. Each channel junction canbe a point of droplet generation. The channel segment 402 from thechannel structure 400 in FIG. 4 and any description to the componentsthereof may correspond to a given channel segment of the plurality ofchannel segments 502 in channel structure 500 and any description to thecorresponding components thereof. The reservoir 404 from the channelstructure 400 and any description to the components thereof maycorrespond to the reservoir 504 from the channel structure 500 and anydescription to the corresponding components thereof.

Each channel segment of the plurality of channel segments 502 maycomprise an aqueous fluid 508 that includes suspended beads 512. Thereservoir 504 may comprise a second fluid 510 that is immiscible withthe aqueous fluid 508. In some instances, the second fluid 510 may notbe subjected to and/or directed to any flow in or out of the reservoir504. For example, the second fluid 510 may be substantially stationaryin the reservoir 504. In some instances, the second fluid 510 may besubjected to flow within the reservoir 504, but not in or out of thereservoir 504, such as via application of pressure to the reservoir 504and/or as affected by the incoming flow of the aqueous fluid 508 at thejunctions. Alternatively, the second fluid 510 may be subjected and/ordirected to flow in or out of the reservoir 504. For example, thereservoir 504 can be a channel directing the second fluid 510 fromupstream to downstream, transporting the generated droplets.

In operation, the aqueous fluid 508 that includes suspended beads 512may be transported along the plurality of channel segments 502 into theplurality of junctions 506 to meet the second fluid 510 in the reservoir504 to create droplets 516, 518. A droplet may form from each channelsegment at each corresponding junction with the reservoir 504. At thejunction where the aqueous fluid 508 and the second fluid 510 meet,droplets can form based on factors such as the hydrodynamic forces atthe junction, flow rates of the two fluids 508, 510, fluid properties,and certain geometric parameters (e.g., w, h₀, α, etc.) of the channelstructure 500, as described elsewhere herein. A plurality of dropletscan be collected in the reservoir 504 by continuously injecting theaqueous fluid 508 from the plurality of channel segments 502 through theplurality of junctions 506. Throughput may significantly increase withthe parallel channel configuration of channel structure 500. Forexample, a channel structure having five inlet channel segmentscomprising the aqueous fluid 508 may generate droplets five times asfrequently than a channel structure having one inlet channel segment,provided that the fluid flow rate in the channel segments aresubstantially the same. The fluid flow rate in the different inletchannel segments may or may not be substantially the same. A channelstructure may have as many parallel channel segments as is practical andallowed for the size of the reservoir. For example, the channelstructure may have at least about 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30,40, 50, 60, 70, 80, 90, 100, 150, 500, 250, 300, 350, 400, 450, 500,600, 700, 800, 900, 1000, 1500, 5000 or more parallel or substantiallyparallel channel segments.

The geometric parameters, w, h₀, and α, may or may not be uniform foreach of the channel segments in the plurality of channel segments 502.For example, each channel segment may have the same or different widthsat or near its respective channel junction with the reservoir 504. Forexample, each channel segment may have the same or different height ator near its respective channel junction with the reservoir 504. Inanother example, the reservoir 504 may have the same or differentexpansion angle at the different channel junctions with the plurality ofchannel segments 502. When the geometric parameters are uniform,beneficially, droplet size may also be controlled to be uniform evenwith the increased throughput. In some instances, when it is desirableto have a different distribution of droplet sizes, the geometricparameters for the plurality of channel segments 502 may be variedaccordingly.

In some instances, at least about 50% of the droplets generated can haveuniform size. In some instances, at least about 55%, 60%, 65%, 70%, 75%,80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or greater of the dropletsgenerated can have uniform size. Alternatively, less than about 50% ofthe droplets generated can have uniform size.

FIG. 6 shows another example of a microfluidic channel structure forincreased droplet generation throughput. A microfluidic channelstructure 600 can comprise a plurality of channel segments 602 arrangedgenerally circularly around the perimeter of a reservoir 604. Each ofthe plurality of channel segments 602 may be in fluid communication withthe reservoir 604. The channel structure 600 can comprise a plurality ofchannel junctions 606 between the plurality of channel segments 602 andthe reservoir 604. Each channel junction can be a point of dropletgeneration. The channel segment 402 from the channel structure 400 inFIG. 2 and any description to the components thereof may correspond to agiven channel segment of the plurality of channel segments 602 inchannel structure 600 and any description to the correspondingcomponents thereof. The reservoir 404 from the channel structure 400 andany description to the components thereof may correspond to thereservoir 604 from the channel structure 600 and any description to thecorresponding components thereof.

Each channel segment of the plurality of channel segments 602 maycomprise an aqueous fluid 608 that includes suspended beads 612. Thereservoir 604 may comprise a second fluid 610 that is immiscible withthe aqueous fluid 608. In some instances, the second fluid 610 may notbe subjected to and/or directed to any flow in or out of the reservoir604. For example, the second fluid 610 may be substantially stationaryin the reservoir 604. In some instances, the second fluid 610 may besubjected to flow within the reservoir 604, but not in or out of thereservoir 604, such as via application of pressure to the reservoir 604and/or as affected by the incoming flow of the aqueous fluid 608 at thejunctions. Alternatively, the second fluid 610 may be subjected and/ordirected to flow in or out of the reservoir 604. For example, thereservoir 604 can be a channel directing the second fluid 610 fromupstream to downstream, transporting the generated droplets.

In operation, the aqueous fluid 608 that includes suspended beads 612may be transported along the plurality of channel segments 602 into theplurality of junctions 606 to meet the second fluid 610 in the reservoir604 to create a plurality of droplets 616. A droplet may form from eachchannel segment at each corresponding junction with the reservoir 604.At the junction where the aqueous fluid 608 and the second fluid 610meet, droplets can form based on factors such as the hydrodynamic forcesat the junction, flow rates of the two fluids 608, 610, fluidproperties, and certain geometric parameters (e.g., widths and heightsof the channel segments 602, expansion angle of the reservoir 604, etc.)of the channel structure 600, as described elsewhere herein. A pluralityof droplets can be collected in the reservoir 604 by continuouslyinjecting the aqueous fluid 608 from the plurality of channel segments602 through the plurality of junctions 606. Throughput may significantlyincrease with the substantially parallel channel configuration of thechannel structure 600. A channel structure may have as manysubstantially parallel channel segments as is practical and allowed forby the size of the reservoir. For example, the channel structure mayhave at least about 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70,80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900,1000, 1500, 5000 or more parallel or substantially parallel channelsegments. The plurality of channel segments may be substantially evenlyspaced apart, for example, around an edge or perimeter of the reservoir.Alternatively, the spacing of the plurality of channel segments may beuneven.

The reservoir 604 may have an expansion angle, a (not shown in FIG. 6)at or near each channel junction. Each channel segment of the pluralityof channel segments 602 may have a width, w, and a height, h₀, at ornear the channel junction. The geometric parameters, w, h₀, and α, mayor may not be uniform for each of the channel segments in the pluralityof channel segments 602. For example, each channel segment may have thesame or different widths at or near its respective channel junction withthe reservoir 604. For example, each channel segment may have the sameor different height at or near its respective channel junction with thereservoir 604.

The reservoir 604 may have the same or different expansion angle at thedifferent channel junctions with the plurality of channel segments 602.For example, a circular reservoir (as shown in FIG. 6) may have aconical, dome-like, or hemispherical ceiling (e.g., top wall) to providethe same or substantially same expansion angle for each channel segments602 at or near the plurality of channel junctions 606. When thegeometric parameters are uniform, beneficially, resulting droplet sizemay be controlled to be uniform even with the increased throughput. Insome instances, when it is desirable to have a different distribution ofdroplet sizes, the geometric parameters for the plurality of channelsegments 602 may be varied accordingly.

In some instances, at least about 50% of the droplets generated can haveuniform size. In some instances, at least about 55%, 60%, 65%, 70%, 75%,80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or greater of the dropletsgenerated can have uniform size. Alternatively, less than about 50% ofthe droplets generated can have uniform size. The beads and/orbiological particle injected into the droplets may or may not haveuniform size.

FIG. 7A shows a cross-section view of another example of a microfluidicchannel structure with a geometric feature for controlled partitioning.A channel structure 700 can include a channel segment 702 communicatingat a channel junction 706 (or intersection) with a reservoir 704. Insome instances, the channel structure 700 and one or more of itscomponents can correspond to the channel structure 100 and one or moreof its components. FIG. 7B shows a perspective view of the channelstructure 700 of FIG. 7A.

An aqueous fluid 712 comprising a plurality of particles 716 may betransported along the channel segment 702 into the junction 706 to meeta second fluid 714 (e.g., oil, etc.) that is immiscible with the aqueousfluid 712 in the reservoir 704 to create droplets 720 of the aqueousfluid 712 flowing into the reservoir 704. At the junction 706 where theaqueous fluid 712 and the second fluid 714 meet, droplets can form basedon factors such as the hydrodynamic forces at the junction 706, relativeflow rates of the two fluids 712, 714, fluid properties, and certaingeometric parameters (e.g., Δh, etc.) of the channel structure 700. Aplurality of droplets can be collected in the reservoir 704 bycontinuously injecting the aqueous fluid 712 from the channel segment702 at the junction 706.

A discrete droplet generated may comprise one or more particles of theplurality of particles 716. As described elsewhere herein, a particlemay be any particle, such as a bead, cell bead, gel bead, biologicalparticle, macromolecular constituents of biological particle, or otherparticles. Alternatively, a discrete droplet generated may not includeany particles.

In some instances, the aqueous fluid 712 can have a substantiallyuniform concentration or frequency of particles 716. As describedelsewhere herein (e.g., with reference to FIG. 4), the particles 716(e.g., beads) can be introduced into the channel segment 702 from aseparate channel (not shown in FIG. 7). The frequency of particles 716in the channel segment 702 may be controlled by controlling thefrequency in which the particles 716 are introduced into the channelsegment 702 and/or the relative flow rates of the fluids in the channelsegment 702 and the separate channel. In some instances, the particles716 can be introduced into the channel segment 702 from a plurality ofdifferent channels, and the frequency controlled accordingly. In someinstances, different particles may be introduced via separate channels.For example, a first separate channel can introduce beads and a secondseparate channel can introduce biological particles into the channelsegment 702. The first separate channel introducing the beads may beupstream or downstream of the second separate channel introducing thebiological particles.

In some instances, the second fluid 714 may not be subjected to and/ordirected to any flow in or out of the reservoir 704. For example, thesecond fluid 714 may be substantially stationary in the reservoir 704.In some instances, the second fluid 714 may be subjected to flow withinthe reservoir 704, but not in or out of the reservoir 704, such as viaapplication of pressure to the reservoir 704 and/or as affected by theincoming flow of the aqueous fluid 712 at the junction 706.Alternatively, the second fluid 714 may be subjected and/or directed toflow in or out of the reservoir 704. For example, the reservoir 704 canbe a channel directing the second fluid 714 from upstream to downstream,transporting the generated droplets.

The channel structure 700 at or near the junction 706 may have certaingeometric features that at least partly determine the sizes and/orshapes of the droplets formed by the channel structure 700. The channelsegment 702 can have a first cross-section height, h₁, and the reservoir704 can have a second cross-section height, h₂. The first cross-sectionheight, h₁, and the second cross-section height, h₂, may be different,such that at the junction 706, there is a height difference of Δh. Thesecond cross-section height, h₂, may be greater than the firstcross-section height, h₁. In some instances, the reservoir maythereafter gradually increase in cross-section height, for example, themore distant it is from the junction 706. In some instances, thecross-section height of the reservoir may increase in accordance withexpansion angle, β, at or near the junction 706. The height difference,Δh, and/or expansion angle, β, can allow the tongue (portion of theaqueous fluid 712 leaving channel segment 702 at junction 706 andentering the reservoir 704 before droplet formation) to increase indepth and facilitate decrease in curvature of the intermediately formeddroplet. For example, droplet size may decrease with increasing heightdifference and/or increasing expansion angle.

The height difference, Δh, can be at least about 1 μm. Alternatively,the height difference can be at least about 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, 50, 60,70, 80, 90, 100, 200, 300, 400, 500 μm or more. Alternatively, theheight difference can be at most about 500, 400, 300, 200, 100, 90, 80,70, 60, 50, 45, 40, 35, 30, 25, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11,10, 9, 8, 7, 6, 5, 4, 3, 2, 1 μm or less. In some instances, theexpansion angle, β, may be between a range of from about 0.5° to about4°, from about 0.1° to about 10°, or from about 0° to about 90°. Forexample, the expansion angle can be at least about 0.01°, 0.1°, 0.2°,0.3°, 0.4°, 0.5°, 0.6°, 0.7°, 0.8°, 0.9°, 1°, 2°, 3°, 4°, 5°, 6°, 7°,8°, 9°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°,75°, 80°, 85°, or higher. In some instances, the expansion angle can beat most about 89°, 88°, 87°, 86°, 85°, 84°, 83°, 82°, 81°, 80°, 75°,70°, 65°, 60°, 55°, 50°, 45°, 40°, 35°, 30°, 25°, 20°, 15°, 10°, 9°, 8°,7°, 6°, 5°, 4°, 3°, 2°, 1°, 0.1°, 0.01°, or less.

In some instances, the flow rate of the aqueous fluid 712 entering thejunction 706 can be between about 0.04 microliters (μL)/minute (min) andabout 40 μL/min. In some instances, the flow rate of the aqueous fluid712 entering the junction 706 can be between about 0.01 microliters(μL)/minute (min) and about 100 μL/min. Alternatively, the flow rate ofthe aqueous fluid 712 entering the junction 706 can be less than about0.01 μL/min. Alternatively, the flow rate of the aqueous fluid 712entering the junction 706 can be greater than about 40 μL/min, such as45 μL/min, 50 μL/min, 55 μL/min, 60 μL/min, 65 μL/min, 70 μL/min, 75μL/min, 80 μL/min, 85 μL/min, 90 μL/min, 95 μL/min, 100 μL/min, 110μL/min, 120 μL/min, 130 μL/min, 140 μL/min, 150 μL/min, or greater. Atlower flow rates, such as flow rates of about less than or equal to 10microliters/minute, the droplet radius may not be dependent on the flowrate of the aqueous fluid 712 entering the junction 706. The secondfluid 714 may be stationary, or substantially stationary, in thereservoir 704. Alternatively, the second fluid 714 may be flowing, suchas at the above flow rates described for the aqueous fluid 712.

In some instances, at least about 50% of the droplets generated can haveuniform size. In some instances, at least about 55%, 60%, 65%, 70%, 75%,80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or greater of the dropletsgenerated can have uniform size. Alternatively, less than about 50% ofthe droplets generated can have uniform size.

While FIGS. 7A and 7B illustrate the height difference, zlh, beingabrupt at the junction 706 (e.g., a step increase), the heightdifference may increase gradually (e.g., from about 0 μm to a maximumheight difference). Alternatively, the height difference may decreasegradually (e.g., taper) from a maximum height difference. A gradualincrease or decrease in height difference, as used herein, may refer toa continuous incremental increase or decrease in height difference,wherein an angle between any one differential segment of a heightprofile and an immediately adjacent differential segment of the heightprofile is greater than 90°. For example, at the junction 706, a bottomwall of the channel and a bottom wall of the reservoir can meet at anangle greater than 90°. Alternatively or in addition, a top wall (e.g.,ceiling) of the channel and a top wall (e.g., ceiling) of the reservoircan meet an angle greater than 90°. A gradual increase or decrease maybe linear or non-linear (e.g., exponential, sinusoidal, etc.).Alternatively or in addition, the height difference may variablyincrease and/or decrease linearly or non-linearly. While FIGS. 7A and 7Billustrate the expanding reservoir cross-section height as linear (e.g.,constant expansion angle, β), the cross-section height may expandnon-linearly. For example, the reservoir may be defined at leastpartially by a dome-like (e.g., hemispherical) shape having variableexpansion angles. The cross-section height may expand in any shape.

The channel networks, e.g., as described above or elsewhere herein, canbe fluidly coupled to appropriate fluidic components. For example, theinlet channel segments are fluidly coupled to appropriate sources of thematerials they are to deliver to a channel junction. These sources mayinclude any of a variety of different fluidic components, from simplereservoirs defined in or connected to a body structure of a microfluidicdevice, to fluid conduits that deliver fluids from off-device sources,manifolds, fluid flow units (e.g., actuators, pumps, compressors) or thelike. Likewise, the outlet channel segment (e.g., channel segment 208,reservoir 604, etc.) may be fluidly coupled to a receiving vessel orconduit for the partitioned cells for subsequent processing. Again, thismay be a reservoir defined in the body of a microfluidic device, or itmay be a fluidic conduit for delivering the partitioned cells to asubsequent process operation, instrument or component.

The methods and systems described herein may be used to greatly increasethe efficiency of single cell applications and/or other applicationsreceiving droplet-based input. For example, following the sorting ofoccupied cells and/or appropriately-sized cells, subsequent operationsthat can be performed can include generation of amplification products,purification (e.g., via solid phase reversible immobilization (SPRI)),further processing (e.g., shearing, ligation of functional sequences,and subsequent amplification (e.g., via PCR)). These operations mayoccur in bulk (e.g., outside the partition). In the case where apartition is a droplet in an emulsion, the emulsion can be broken andthe contents of the droplet pooled for additional operations. Additionalreagents that may be co-partitioned along with the barcode bearing beadmay include oligonucleotides to block ribosomal RNA (rRNA) and nucleasesto digest genomic DNA from cells. Alternatively, rRNA removal agents maybe applied during additional processing operations. The configuration ofthe constructs generated by such a method can help minimize (or avoid)sequencing of the poly-T sequence during sequencing and/or sequence the5′ end of a polynucleotide sequence. The amplification products, forexample, first amplification products and/or second amplificationproducts, may be subject to sequencing for sequence analysis. In somecases, amplification may be performed using the Partial HairpinAmplification for Sequencing (PHASE) method.

A variety of applications require the evaluation of the presence andquantification of different biological particle or organism types withina population of biological particles, including, for example, microbiomeanalysis and characterization, environmental testing, food safetytesting, epidemiological analysis, e.g., in tracing contamination or thelike.

Computer Systems

The present disclosure provides computer systems that are programmed toimplement methods of the disclosure. FIG. 11 shows a computer system1101 that is programmed or otherwise configured to (i) control amicrofluidics system (e.g., fluid flow), such as for controlledpartitioning, sorting (e.g., of an analyte, of a partition, of a cell,etc.), polymerization, application of one or more stimuli, and the like,(ii) generate and maintain a library or a plurality of libraries ofbarcodes, (iii) perform sequencing, and/or (iv) analyze and/or outputresults of such sequencing. The computer system 1101 can regulatevarious aspects of the present disclosure, such as, for example,regulating fluid flow rate in one or more channels in a microfluidicstructure, regulating one or more reactions or interactions of ananalyte, biological particle, and/or a sample, regulating the sorting ofone or more analytes, and/or regulating the generation of one or morelibraries. The computer system 1101 can be an electronic device of auser or a computer system that is remotely located with respect to theelectronic device. The electronic device can be a mobile electronicdevice.

The computer system 1101 includes a central processing unit (CPU, also“processor” and “computer processor” herein) 1105, which can be a singlecore or multi core processor, or a plurality of processors for parallelprocessing. The computer system 1101 also includes memory or memorylocation 1110 (e.g., random-access memory, read-only memory, flashmemory), electronic storage unit 1115 (e.g., hard disk), communicationinterface 1120 (e.g., network adapter) for communicating with one ormore other systems, and peripheral devices 1125, such as cache, othermemory, data storage and/or electronic display adapters. The memory1110, storage unit 1115, interface 1120 and peripheral devices 1125 arein communication with the CPU 1105 through a communication bus (solidlines), such as a motherboard. The storage unit 1115 can be a datastorage unit (or data repository) for storing data. The computer system1101 can be operatively coupled to a computer network (“network”) 1130with the aid of the communication interface 1120. The network 1130 canbe the Internet, an internet and/or extranet, or an intranet and/orextranet that is in communication with the Internet. The network 1130 insome cases is a telecommunication and/or data network. The network 1130can include one or more computer servers, which can enable distributedcomputing, such as cloud computing. The network 1130, in some cases withthe aid of the computer system 1101, can implement a peer-to-peernetwork, which may enable devices coupled to the computer system 1101 tobehave as a client or a server.

The CPU 1105 can execute a sequence of machine-readable instructions,which can be embodied in a program or software. The instructions may bestored in a memory location, such as the memory 1110. The instructionscan be directed to the CPU 1105, which can subsequently program orotherwise configure the CPU 1105 to implement methods of the presentdisclosure. Examples of operations performed by the CPU 1105 can includefetch, decode, execute, and writeback.

The CPU 1105 can be part of a circuit, such as an integrated circuit.One or more other components of the system 1101 can be included in thecircuit. In some cases, the circuit is an application specificintegrated circuit (ASIC).

The storage unit 1115 can store files, such as drivers, libraries andsaved programs. The storage unit 1115 can store user data, e.g., userpreferences and user programs. The computer system 1101 in some casescan include one or more additional data storage units that are externalto the computer system 1101, such as located on a remote server that isin communication with the computer system 1101 through an intranet orthe Internet.

The computer system 1101 can communicate with one or more remotecomputer systems through the network 1130. For instance, the computersystem 1101 can communicate with a remote computer system of a user(e.g., operator). Examples of remote computer systems include personalcomputers (e.g., portable PC), slate or tablet PC's (e.g., Apple® iPad,Samsung® Galaxy Tab), telephones, Smart phones (e.g., Apple® iPhone,Android-enabled device, Blackberry®), or personal digital assistants.The user can access the computer system 1101 via the network 1130.

Methods as described herein can be implemented by way of machine (e.g.,computer processor) executable code stored on an electronic storagelocation of the computer system 1101, such as, for example, on thememory 1110 or electronic storage unit 1115. The machine executable ormachine readable code can be provided in the form of software. Duringuse, the code can be executed by the processor 1105. In some cases, thecode can be retrieved from the storage unit 1115 and stored on thememory 1110 for ready access by the processor 1105. In some situations,the electronic storage unit 1115 can be precluded, andmachine-executable instructions are stored on memory 1110.

The code can be pre-compiled and configured for use with a machinehaving a processor adapted to execute the code, or can be compiledduring runtime. The code can be supplied in a programming language thatcan be selected to enable the code to execute in a pre-compiled oras-compiled fashion.

Aspects of the systems and methods provided herein, such as the computersystem 1101, can be embodied in programming. Various aspects of thetechnology may be thought of as “products” or “articles of manufacture”typically in the form of machine (or processor) executable code and/orassociated data that is carried on or embodied in a type of machinereadable medium. Machine-executable code can be stored on an electronicstorage unit, such as memory (e.g., read-only memory, random-accessmemory, flash memory) or a hard disk. “Storage” type media can includeany or all of the tangible memory of the computers, processors or thelike, or associated modules thereof, such as various semiconductormemories, tape drives, disk drives and the like, which may providenon-transitory storage at any time for the software programming. All orportions of the software may at times be communicated through theInternet or various other telecommunication networks. Suchcommunications, for example, may enable loading of the software from onecomputer or processor into another, for example, from a managementserver or host computer into the computer platform of an applicationserver. Thus, another type of media that may bear the software elementsincludes optical, electrical and electromagnetic waves, such as usedacross physical interfaces between local devices, through wired andoptical landline networks and over various air-links. The physicalelements that carry such waves, such as wired or wireless links, opticallinks or the like, also may be considered as media bearing the software.As used herein, unless restricted to non-transitory, tangible “storage”media, terms such as computer or machine “readable medium” refer to anymedium that participates in providing instructions to a processor forexecution.

Hence, a machine readable medium, such as computer-executable code, maytake many forms, including but not limited to, a tangible storagemedium, a carrier wave medium or physical transmission medium.Non-volatile storage media include, for example, optical or magneticdisks, such as any of the storage devices in any computer(s) or thelike, such as may be used to implement the databases, etc. shown in thedrawings. Volatile storage media include dynamic memory, such as mainmemory of such a computer platform. Tangible transmission media includecoaxial cables; copper wire and fiber optics, including the wires thatcomprise a bus within a computer system. Carrier-wave transmission mediamay take the form of electric or electromagnetic signals, or acoustic orlight waves such as those generated during radio frequency (RF) andinfrared (IR) data communications. Common forms of computer-readablemedia therefore include for example: a floppy disk, a flexible disk,hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD orDVD-ROM, any other optical medium, punch cards paper tape, any otherphysical storage medium with patterns of holes, a RAM, a ROM, a PROM andEPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wavetransporting data or instructions, cables or links transporting such acarrier wave, or any other medium from which a computer may readprogramming code and/or data. Many of these forms of computer readablemedia may be involved in carrying one or more sequences of one or moreinstructions to a processor for execution.

The computer system 1101 can include or be in communication with anelectronic display 1135 that comprises a user interface (UI) 1140 forproviding, for example, results of sequencing analysis. Examples of UIsinclude, without limitation, a graphical user interface (GUI) andweb-based user interface.

Methods and systems of the present disclosure can be implemented by wayof one or more algorithms. An algorithm can be implemented by way ofsoftware upon execution by the central processing unit 1105. Thealgorithm can, for example, perform sequencing and process libraries,such as by accessing one or more databases.

Devices, systems, compositions and methods of the present disclosure maybe used for various applications, such as, for example, processing asingle analyte (e.g., RNA, DNA, metabolite, protein, etc.) or multipleanalytes (e.g., DNA and RNA, DNA and protein, RNA and protein, or RNA,DNA and protein, etc.) from a single cell. For example, a biologicalparticle (e.g., a cell or cell bead) is partitioned in a partition(e.g., droplet), and multiple analytes from the biological particle areprocessed for subsequent processing. The multiple analytes may be fromthe single cell. This may enable, for example, simultaneous proteomic,transcriptomic and genomic analysis of the cell.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. It is not intendedthat the invention be limited by the specific examples provided withinthe specification. While the invention has been described with referenceto the aforementioned specification, the descriptions and illustrationsof the embodiments herein are not meant to be construed in a limitingsense. Numerous variations, changes, and substitutions will now occur tothose skilled in the art without departing from the invention.Furthermore, it shall be understood that all aspects of the inventionare not limited to the specific depictions, configurations or relativeproportions set forth herein which depend upon a variety of conditionsand variables. It should be understood that various alternatives to theembodiments of the invention described herein may be employed inpracticing the invention. It is therefore contemplated that theinvention shall also cover any such alternatives, modifications,variations or equivalents. It is intended that the following claimsdefine the scope of the invention and that methods and structures withinthe scope of these claims and their equivalents be covered thereby.

1-50. (canceled)
 51. A method for identifying an intracellular protein,comprising: (a) contacting a cell bead comprising said intracellularprotein from a cell with an antibody having a binding specificity tosaid intracellular protein, wherein said antibody is coupled to a firstnucleic acid barcode molecule comprising a first nucleic acid sequence;(b) partitioning said cell bead and a bead in a partition, wherein saidbead comprises a second nucleic acid barcode molecule comprising asecond nucleic acid sequence; and (c) using said first nucleic acidbarcode molecule and said second nucleic acid barcode molecule togenerate a composite nucleic acid molecule comprising said first nucleicacid sequence and said second nucleic acid sequence.
 52. The method ofclaim 51, further comprising, subsequent to (a), washing out unboundantibodies from said cell bead.
 53. The method of claim 51, wherein (a)is performed under conditions sufficient to permit said antibody to flowinto said cell bead and couple to said intracellular protein.
 54. Themethod of claim 51, wherein subsequent to (c), said method furthercomprises: (d) sequencing said composite nucleic acid molecule orderivative thereof to identify said first nucleic acid sequence and saidsecond nucleic acid sequence, wherein said first nucleic acid sequenceidentifies said intracellular protein and said second nucleic acidsequence identifies said cell bead.
 55. The method of claim 51, whereinprior to (a), said method comprises generating said cell bead comprisingsaid cell.
 56. The method of claim 55, wherein generating cell beadcomprises (i) providing a mixture comprising said cell and a pluralityof monomeric or polymeric precursors, and (ii) polymerizing saidmonomeric or polymeric precursors to form said cell bead.
 57. The methodof claim 56, further comprising lysing said cell within said cell bead.58. The method of claim 51, further comprising releasing said secondnucleic acid barcode molecule from said bead.
 59. The method of claim51, wherein said bead comprises a plurality of nucleic acid barcodemolecules, each of said plurality of nucleic acid barcode moleculescomprising said second nucleic acid sequence.
 60. The method of claim59, wherein each of said plurality of nucleic acid barcode moleculescomprises a unique nucleic acid sequence that is unique to said each ofsaid plurality of nucleic acid barcode molecules.
 61. The method ofclaim 51, further wherein said cell bead comprises a secondintracellular protein from said cell, and wherein (a) comprises bringingsaid cell bead in contact with a second antibody having a bindingspecificity to said second intracellular protein, wherein said secondantibody-is coupled to a third nucleic acid barcode molecule comprisinga third nucleic acid sequence different from said first nucleic acidsequence.
 62. The method of claim 61, wherein (c) further comprisesusing said third nucleic acid barcode molecule and said second nucleicacid barcode molecule to generate a second composite nucleic acidmolecule comprising said third nucleic acid sequence and said secondnucleic acid sequence, and the method further comprises (d) sequencingsaid second composite nucleic acid molecule or derivative thereof toidentify said third nucleic acid sequence and said second nucleic acidsequence, wherein said third nucleic acid sequence identifies saidsecond intracellular protein and said second nucleic acid sequenceidentifies said cell bead.
 63. The method of claim 62, wherein saidsecond intracellular protein is different than said intracellularprotein.
 64. The method of claim 51, wherein said partition is anaqueous droplet in an emulsion.
 65. The method of claim 51, wherein saidfirst nucleic acid sequence comprises a barcode sequence that identifiessaid antibody.
 66. The method of claim 51, wherein said second nucleicacid barcode molecule further comprises one or more additional sequencesselected from the group consisting of: a sequence for attachment to asequencing flow cell, a primer sequence, and an anchoring sequence. 67.A method for determining that a cell surface-bound analyte and anintracellular analyte originated from a cell, comprising: (a) binding afirst antibody to said cell surface-bound analyte of said cell, or aderivative said cell, wherein said first antibody comprises a firstnucleic acid barcode molecule comprising a first nucleic acid sequence;(b) binding a second antibody to said intracellular analyte of saidcell, or a derivative said cell, wherein said second antibody comprisesa second nucleic acid barcode molecule comprising a second nucleic acidsequence; and (c) providing a plurality of nucleic acid barcodemolecules comprising a common barcode sequence and generating (i) afirst barcoded nucleic acid molecule comprising said first nucleic acidsequence and said common barcode sequence and (ii) a second barcodednucleic acid molecule comprising said second nucleic acid sequence andsaid common barcode sequence.
 68. The method of claim 67, wherein thefurther comprises (d) sequencing said first barcoded nucleic acidmolecule, or a derivative thereof, and said second barcoded nucleic acidmolecule, or a derivative thereof, to identify said first nucleic acidsequence, said second nucleic acid sequence, and said common barcodesequence, wherein said first nucleic acid sequence identifies said cellsurface-bound analyte, said second nucleic acid sequence identifies saidintracellular analyte, and said common barcode sequence identifies saidcell.
 69. The method of claim 67, wherein (a) comprises contacting saidcell with said first antibody to couple said first antibody with saidcell surface-bound analyte and (b) comprises (i) generating a cell beadcomprising said cell and said intracellular analyte, and (ii) contactingsaid cell bead with said second antibody to couple and said secondantibody with said intracellular analyte.
 70. The method of claim 67,wherein prior to (a), said method comprises generating a cell beadcomprising said cell, wherein said cell bead comprises said cellsurface-bound analyte and said intracellular analyte, and wherein (a)comprises contacting said cell bead with said first antibody to couplesaid first antibody with said cell surface-bound analyte and (b)comprises contacting said cell bead with said second antibody to coupleand said second antibody with said intracellular analyte.
 71. The methodof claim 67, wherein (c) comprises partitioning said first antibodycoupled with said cell surface-bound analyte and said second antibodycoupled with said intracellular analyte with said plurality of nucleicacid barcode molecules.
 72. The method of claim 71, wherein saidplurality of nucleic acid barcode molecules is coupled to a bead. 73.The method of claim 67, wherein said cell surface-bound analyte and saidintracellular analyte are different types of analytes.
 74. The method ofclaim 67, wherein said cell surface-bound analyte and said intracellularanalyte are the same type of analyte.
 75. The method of claim 67,wherein said cell surface-bound analyte and/or said intracellularanalyte is a protein.